Compact fluorescent lamp, self-ballasted fluorescent lamp and luminaire

ABSTRACT

A compact self-ballasted fluorescent lamp ( 10 ) which is equivalent to a typical light bulb is provided.  
     The self-ballasted fluorescent lamp ( 10 ) includes a cover ( 14 ), a lighting circuit ( 16 ), an arc tube ( 18 ), a base ( 12 ) and a globe ( 17 ) and formed into a shape whose outline dimensions are nearly identical to the standard dimensions of a typical light bulb. The arc tube ( 18 ) is comprised of a plurality of U-shaped bent bulbs ( 31 ) which have an inner tube diameter ranging from 6 to 9 mm and arranged in parallel with one another. Having a bulb height ranging from 50 to 60 mm and a discharge path from 20 to 300 mm long, the arc tube ( 18 ) is designed such that the total luminous flux is not less than  700  lm with a lamp efficiency of not less than  60  lm/W when the lamp is lit at the lamp power of  7  to  15  W. An envelope ( 19 ) comprising the cover. ( 14 ) and the globe ( 17 ) has a height ranging from 110 to 125 mm, including the height of the base ( 12 ).

TECHNICAL FIELD

[0001] The present invention relates to a compact fluorescent lamp and aself-ballasted fluorescent lamp which are made to an even smaller scale,and also relates to a luminaire.

BACKGROUND ART

[0002] Examples of conventionally known self-ballasted fluorescent lampsinclude a self-ballasted fluorescent lamp which is provided with acover, a lighting circuit contained in the cover, and an arc tube bentor otherwise formed into an appropriate shape and contained in a globe,said cover having a base that can be mounted in a socket designed for atypical light bulb.

[0003] A self-ballasted fluorescent lamp commercially available atpresent typically has such specifications as a height of approximately130 mm (including the height of the base), an outer diameter ofapproximately 70 mm, an outer tube diameter of the arc tube ofapproximately 12 mm, a discharge path length of approximately 280 mm, atube wall thickness of not less than 1.1 mm, and a lamp power ofapproximately 13 W. Due to its configuration, however, it is difficultto provide a fluorescent lamp which has such an arc tube and is ascompact as typical light bulb. Nevertheless, there is an increasingdemand for fluorescent lamps made to an even smaller scale.

[0004] Another example of self-ballasted fluorescent lamps is disclosedin Japanese Patent Laid-open No. 1987-12051, which relates to afluorescent lamp, wherein an arc tube having three U-shaped bent bulbsis disposed in such a way that the three U-shaped bent bulbsrespectively correspond to the three sides of an approximatelyequilateral triangle. However, as there is no detailed discussion in theabove Japanese Patent Public Disclosure as to various criteria regardingthe reduction of the dimensions of the lamp, such as dimensions and theshape of the arc tube as well as criteria for lighting the lamp, theinvention disclosed in said publication does not provide the optimumconfiguration for reducing the dimensions of the lamp.

[0005] Another example of fluorescent lamps is disclosed in JapanesePatent Laid-open No. 1987-12051, wherein the arc tube of the fluorescentlamp is formed in a U-like shape having corners bent at approximately90°. However, the configuration having such an arc tube, i.e. an arctube having sharp corners, presents a problem of irregularity inluminance, because the corners of the arc tube are too close to theglobe when the arc tube is contained in the globe which is as small asthat of a typical light bulb.

[0006] Another example of fluorescent lamps is disclosed in JapanesePatent Laid-open No. 1997-69309, wherein the arc tube is bent into aspiral or other shape so as to produce a lamp having a shape anddimensions nearly identical to those of a typical light bulb. However, aconfiguration which calls for bending the arc tube into such acomplicated shape as a spiral requires a complicated production processand presents a problem in that reduction of production costs isdifficult. As it is difficult to put such an arc tube in practical usefor reasons described above, an arc tube having U-shaped bent bulbs isnormally used. However, a lamp having such an arc tube, too, isdifficult to be made compact, because it imposes various limitations inthe shape and the dimensions of the U-shaped bent bulbs.

[0007] When the dimensions of a fluorescent lamp are reduced, therearises the danger of heat from the arc tube exerting an unfavorableinfluence on the lighting circuit that is contained in the cover. As afluorescent lamp disclosed in Japanese Patent Laid-open No. 1996-273615,one of the known ways to solve this problem is a configuration whichcalls for disposing a circuit board for mounting components of thelighting circuit thereon in such a manner that the components arepositioned apart from the ends of the arc tube at which the electrodesare provided. As a result of the reduction of the dimensions offluorescent lamps, however, circuit boards, too, are made compact.Therefore, the above configuration presents a problem in that thereduction in the space in which the necessary components are mountedincreases the planar dimensions of the lamp too much, particularly atthe part where the cover is located.

[0008] Regarding a self-ballasted fluorescent lamp which is providedwith a cover having a base that can be mounted in a socket designed foran incandescent lamp, a lighting circuit contained in the cover, and anarc tube bent or otherwise formed into an appropriate shape andcontained in a globe, a configuration which calls for disposing acircuit board at the base-facing end of an arc tube that is bent in aU-like shape and arranging electrical components on both end of thecircuit board is widely known. One of examples of such configuration isdisclosed in Japanese Patent Laid-open No. 1988-245803. Compared withthe aforementioned configuration which calls for positioning the circuitboard apart from the ends of the arc tube, said configuration disclosedin Japanese Patent Laid-open No. 1988-245803 is more effective inreducing the horizontal dimensions of the lamp at the region of thecover. On the other hand, it presents such problems that interferencebetween the electrical components and the arc tube, especially betweenthe electrical components and the end of the arc tube, increase theinfluence of heat exerted on the electrical components and that such aconfiguration makes the lamp too long.

[0009] As described above, the outer diameter of the conventionalself-ballasted fluorescent lamp has larger than the outer diameter oftypical light bulb. Therefore, this configuration presents problem inthat it is not suitable for a luminaire which uses a typical light bulbin place of a typical light bulb.

[0010] Regarding a fluorescent lamp which is used to a self-ballasedfluorescent lamp, a configuration which a bulb has a bent dischargepath, which formed by connecting a three U-shaped tubular bodies inseries and electrodes disposed at the both ends of the bulb is widelyknown. One of examples of such configuration is disclosed in JapanesePatent Laid-open No. 220360-1989. And such configuration ensures thelength of a discharge path and the reduction of the dimensions of afluorescent lamp.

[0011] In some cases, such a fluorescent lamp uses a main amalgam forcontrolling the pressure of the mercury vapor in the bulb within anappropriate range during the time that the lamp is lit under normalconditions and an auxiliary amalgam for absorbing mercury floating inthe bulb when the lamp is turned off and releasing the absorbed mercuryduring the early stage of lighting, including the moment when thelighting is initiated. In a configuration where the amalgams are used,the main amalgam is contained in a minute tube which serves to dischargethe air and projects from an end, i.e. the end at which an electrode iscontained in the bulb, of a tubular body that is located at an end ofthe bulb, while the auxiliary amalgam is disposed at an end of a tubularbody positioned at the middle portion of the bulb. However, when theexhaust minute tube that contains the main amalgam and projects from atubular body situated at an end of the bulb is located at the same endat which an electrode enclosed in the bulb is located, the temperatureof the main amalgam becomes too high due to the influence of the heatfrom the electrode. Such an increase in the temperature of the mainamalgam impairs the effective control of the pressure of the mercuryvapor and causes the pressure of the mercury vapor to increase too much,resulting in a decrease in luminous flux. This configuration presentsanother problem in that it is difficult to uniform or stabilize thepressure of the mercury vapor in the tubular body that is located at theother end of the bulb, at a long distance from the main amalgam.

[0012] Another example of fluorescent lamps characterized by inclusionof a main amalgam is disclosed in Japanese Utility Model Publication No.1992-47893, wherein a main amalgam is disposed in a minute tubeprojecting from an end of one of the three tubular bodies that form thebulb, said tubular body being the middle tubular body of the threetubular bodies. The fluorescent lamp having this configuration iscapable of reducing the influence of the heat from the electrodesexerted on the main amalgam, limiting the pressure of the mercury vaporwithin an appropriate range by preventing an excessive increase intemperature of the main amalgam, and also capable of reducing thedistances from the main amalgam to the respective ends of the bulb by anearly identical degree, thereby making the pressure of the mercuryvapor uniform and stable throughout the interior of the bulb. On theother hand, the above configuration presents a problem in that disposingthe main amalgam in the minute tube projecting from an end of the middletubular body of the three tubular bodies of the bulb positions the mainamalgam too far from the electrodes, making it difficult to warm themain amalgam. Especially at the initiation of lighting, when both theambient temperature around the fluorescent lamp and the temperature ofthe main amalgam itself are low, the main amalgam is slow to releasemercury, because it takes a long time for the temperature of the mainamalgam to reach the level where the main amalgam functions mosteffectively. As a result, the luminous flux build-up characteristicsbecome poor, and it takes an excessively long time to stabilize theluminous flux.

[0013] In response to the recent tendency toward compact fluorescentlamps, the demands for reduction of the dimensions of bulbs are on theincrease. In the configuration where each minute tube for dischargingthe air is provided at an end of the bulb, the reduction of the diameterof the bulb makes it necessary to reduce the diameter of the minutetubes. However, a minute tube having a diameter smaller than a givendimension has poor exhaust conductance, resulting in decrease in theexhaust efficiency. On the other hand, if the diameter of the minutetubes are not reduced, the distance between each minute tube and a pairof inner copper-weld wires that support an electrode is reduced, makingthe operation of sealing the bulb difficult.

[0014] In order to solve the above problems, an object of the presentinvention is to provide a fluorescent lamp and a self-ballastedfluorescent lamp that are characterized by the minutes tubes positionedso as to permit the amalgams to be disposed at the optimum locations andenable the reduction of the diameter of the bulb. Another object of thepresent invention is to provide a self-ballasted fluorescent lamp and aluminaire that enable the reduction of the diameter of the portion nearthe base of the lamp as well as the reduction of the length of the lamp.Yet another object of the present invention is to provide a compactself-ballasted fluorescent lamp which is equivalent to a typical lightbulb and a luminaire including such a self-ballasted fluorescent lamp.

DISCLOSURE OF THE INVENTION

[0015] A fluorescent lamp according to the present invention includes abulb having a bent discharge path, which is formed by connecting aplurality of tubular bodies in series, and a plurality of minute tubeslocated at the middle of the discharge path and communicating therewith;a phosphor applied to the inner surface of the bulb; filler gashermetically contained in the bulb; electrodes respectively disposed atthe two ends of the bulb in such a manner as to be enclosed in thesealed bulb; and an amalgam enclosed in a minute tube closest to eitherelectrode. By enclosing the amalgam in a minute tube which is, of theplurality of minute tubes provided at the middle portion of the bulb,located closest to either electrode, the configuration described aboveprevents the influence of the heat from the electrode from increasingthe temperature of the amalgam too much and also permits the amalgam tobe warmed easily during the initial stage of lighting. As a result, theconfiguration is capable of maintaining the pressure of the mercuryvapor within an appropriate range and reducing the time taken for theluminous flux to become stable when lighting is initiated.

[0016] According to another feature of the invention, the fluorescentlamp has the same configuration as described above except that one ofthe electrodes attached to the two ends of the bulb so as to becontained in the sealed bulb is a preheating-side electrode, i.e. anelectrode disposed at the end where preheating is conducted, while theother electrode is a non-preheating-side electrode, i.e. an electrodedisposed at the end where preheating is not conducted; and that theamalgam is enclosed in the minute tube which is closest to thepreheating-side electrode. As a result, this configuration permits theamalgam to be warmed easily during the initial stage of lighting andalso improves the build-up characteristics of luminous flux.

[0017] In the configuration of a fluorescent lamp described above, byforming the open end portion through which said minute tube communicateswith the corresponding tubular body narrower than the interior of thebody of the minute tube, in which an amalgam will be enclosed, reliableenclosure of the amalgam is ensured.

[0018] According to yet another feature of the invention, a fluorescentlamp includes a bulb having an inner tube diameter ranging from 6 to 9mm and a bent discharge path, which is formed by connecting a pluralityof tubular bodies in series, each tubular body that is located at an endof the bulb being provided with a minute tube formed at thenon-electrode end of the tubular body, i.e. the end where an electrodeis not disposed; a phosphor applied to the inner surface of the bulb;filler gas hermetically contained in the bulb; and electrodesrespectively disposed at the two ends of the bulb in such a manner as tobe enclosed in the sealed bulb. By forming minute tubes for dischargingthe air at the non-electrode ends of the respective tubular bodieslocated at the two ends of the bulb, the configuration described aboveenables a slender bulb with an inner tube, diameter ranging from 6 to 9mm to have a minute tube having a diameter not smaller than a givendimension as well as superior exhaust conductance and exhaust efficiencyat the non-electrode ends of the respective tubular bodies located atthe two ends of the bulb. At the same time, the above configurationfacilitates an operation to dispose electrodes at the electrode-ends ofthe tubular bodies and seal the bulb.

[0019] In the configuration of a fluorescent lamp that has the sameconfiguration as the one described above, by enclosing an amalgam in theminute tube that is provided at the non-electrode end of a tubular bodylocated at an end of the bulb, it is possible to prevent the influenceof the heat from the electrode from increasing the temperature of theamalgam too much and also permit the amalgam to be warmed easily duringthe initial stage of lighting. As a result, it is possible to maintainthe pressure of the mercury vapor within an appropriate range and reducethe time taken for the luminous flux to become stable when lighting isinitiated.

[0020] In the configuration of a fluorescent lamp that has the sameconfiguration as the one described above, by disposing an auxiliaryamalgam in the bulb, it is possible to maintain the pressure of themercury vapor within an appropriate range and reduce the time taken forthe luminous flux to become stable when lighting is initiated.

[0021] In the configuration of a fluorescent lamp that has the sameconfiguration as the one described above, by positioning the tubularbodies of the bulb in such a manner that the tubular bodies respectivelycorrespond to the three sides of a triangle when viewed in a crosssection, the bulb can be made into such a compact shape as to be usableas a compact self-ballasted fluorescent lamp or the like.

[0022] A self-ballasted fluorescent lamp according to the presentinvention includes a fluorescent lamp and a lighting device for lightingthe fluorescent lamp, said fluorescent lamp having a configurationcorresponding to any one of the configurations described above. Thisfeature of the invention is capable of providing a self-ballastedfluorescent lamp which has the same effect as one of the fluorescentlamps described above.

[0023] A self-ballasted fluorescent lamp according to the presentinvention includes an arc tube which is formed by parallely arranging aplurality of U-shaped bent bulbs having an inner tube diameter rangingfrom 6 to 9 mm in such a manner that the height of the bulb and thelength of the discharge path respectively range from 50 to 60 mm andfrom 200 to 300 mm and that the lamp has a total luminous flux of notless than 700 lm and a lamp efficiency of not less than 60 lm/W when thelamp is lit at the lamp power of 7 to 15 W; an envelope having a coverthat includes a base and is adapted to permit said arc tube to beattached thereto, the height of the envelope ranging from 110 to 125 mmincluding the height of the base; and a lighting circuit contained inthe cover. As this configuration includes said arc tube, which is formedby parallely arranging a plurality of U-shaped bent bulbs having aninner tube diameter ranging from 6 to 9 mm in such a manner that theheight of the bulb and the length of the discharge path respectivelyrange from 50 to 60 mm and from 200 to 300 mm and that the lamp has atotal luminous flux of not less than 700 lm and a lamp efficiency of notless than 60 lm/W when the lamp is lit at the lamp power of 7 to 15 W,and limits the height the envelope, which is provided with a coverincluding a base to which the arc tube is attached, in the range from110 to 125 mm, it is possible to determine the optimum criteria for thecomponents to make the dimensions and the total luminous flux of thelamp correspond to those of a typical light bulb for generalillumination, such as an incandescent lamp having a rated power of 60Wtype. The lower limit of the inner tube diameter of the tube is set at 6mm as mentioned above, because the tube having an inner tube diameter ofless than 6 mm requires a considerably high starting voltage and istherefore impractical. The term ‘a total luminous flux’ mentioned aboverefers to a value representing radiation from an entire self-ballastedfluorescent lamp. Therefore, if the self-ballasted fluorescent lampincludes a globe, it represents the result of a measurement conducted inthe state where the globe is attached. Furthermore, ‘a lamp efficiency’is defined as a value based on the lamp power minus the powerconsumption of the lighting circuit.

[0024] According to yet another feature of the invention, aself-ballasted fluorescent lamp includes an arc tube formed by parallelyarranging a plurality of U-shaped bent bulbs, each of which has an outertube diameter ranging from 8 to 11 mm, a tube wall thickness rangingfrom 0.7 to 1.0 mm and a smoothly curved crown; a cover including a basethat is adapted to permit said arc tube to be attached thereto; and alighting circuit contained in the cover. As this configuration includessaid arc tube formed by parallely arranging a plurality of U-shaped bentbulbs, each of which has an outer tube diameter ranging from 8 to 11 mm,a tube wall thickness ranging from 0.7 to 1.0 mm and a smoothly curvedcrown, it is possible to determine such a tube diameter as to make thedimensions and the total luminous flux of the lamp correspond to thoseof a typical light bulb for general illumination, such as anincandescent lamp having a rated power of 60 W type and also determinesuch a range of the thickness of the bulb wall as to enable the increaseof the inner surface area of the bulb while ensuring sufficient strengthwithin the limit of the outer diameter of the bulb determined as above.Further, in order to form each U-shaped bent bulb within the limit ofthe tube wall thickness determined as above, the crown of the U has tobe smoothly curved. Should the crown have a sharp corner or corners, thetube wall at the corner(s) would be too thin to maintain sufficientstrength.

[0025] According to yet another feature of the invention, aself-ballasted fluorescent lamp includes an arc tube formed by parallelyarranging a plurality of U-shaped bent bulbs, each of which has a bentportion and straight portions; a cover including a base that is adaptedto permit said arc tube to be attached thereto; and a lighting circuitwhich includes a circuit board having the maximum width ranging up to1.2 times the maximum width of the arc tube, the maximum width of thearc tube being the dimension along which the U-shaped bent bulbs arearranged, said lighting circuit contained in the cover in such a mannerthat the circuit board is positioned with one of its sides facing allthe ends of the straight portions of the arc tube and provided withcomponents having relatively high heat resistance mounted on the side ofthe circuit board facing the arc tube and components having relativelylow heat resistance mounted on the opposite side of the circuit board.According to the configuration as above, the maximum width of thecircuit board is so set as to range up to 1.2 times the maximumdimension along which the U-shaped bent bulbs of the arc tube arearranged, and the components that have relatively high heat resistanceare mounted on the arc tube facing side of the circuit board, while thecomponents having relatively low heat resistance are mounted on theother side of the circuit board. Thus, the above configuration iscapable of reducing the size of the circuit board while limiting theinfluence that heat exerts on the components mounted on the circuitboard. Consequently, the configuration is capable of reducing thedimensions of the cover, which contains the circuit board, so that theyare equivalent to the dimensions of a typical light bulb. Although it isrecommended that the circuit board have a shape of a circular disk,which is the most effective shape to ensure the space for mounting, thecircuit board may have a polygonal shape, such as a square, or an ovalshape.

[0026] According to yet another feature of the invention, the componentshaving relatively high heat resistance of the fluorescent lamp describedabove are chip-shaped rectifying devices. Therefore, the thermalinfluence from the arc tube can be limited.

[0027] According to yet another feature of the invention, aself-ballasted fluorescent lamp includes a cover having a base; alighting circuit contained in the cover; a globe having a nearlyidentical shape as a typical light bulb and attached to the cover, andan arc tube which is contained in the globe and has three or moreU-shaped bent bulbs, each of which has a smoothly curbed crown, theU-shaped bent bulbs connected to one another in series and arranged sothat their crowns are aligned in a circle and face the inner surface ofthe globe and that the U-shaped bent bulbs are spaced apart at adistance not exceeding the outer diameter of each bulb. As the arc tubehas three or more U-shaped bent bulbs which have smoothly curbed crowns,are connected to one another in series, and positioned apart from oneanother in such a manner that the distance between the bulbs does notexceed the outer diameter of each bulb and that their crowns are alignedin a circle and face the inner surface of the globe, this configurationmakes it possible to dispose the arc tube in the globe that is formed ina compact shape resembling a typical light bulb. This configuration isalso capable of providing more uniform luminosity and more effectiveillumination even if the arc tube is contained in such a compact globe.

[0028] According to yet another feature of the invention, aself-ballasted fluorescent lamp includes an arc tube formed by parallelyarranging a plurality of U-shaped bent bulbs having an outer tubediameter ranging from 8 to 11 mm, the maximum width of the arc tubealong which the U-shaped bent bulbs are arranged ranging from 32 to 43mm; a cover including a base that is adapted to permit said arc tube tobe attached thereto; a lighting circuit contained in the cover; and aglobe having a maximum outer diameter limited in the range from 55 to 60mm and attached to the cover with said arc tube enclosed in the globe insuch a manner that A2>A1≧A3, wherein A1 represents the minimum distancebetween the globe and each crown of the arc tube, A2 the minimumdistance between the maximum diameter portion of the globe and the arctube, and A3 the minimum distance between the base end of the globe andthe arc tube. As a self-ballasted fluorescent lamp includes an arc tubeformed by parallely arranging a plurality of U-shaped bent bulbs havingan outer tube diameter ranging from 8 to 11 mm, the maximum width of thearc tube along which the U-shaped bent bulbs are arranged ranging from32 to 43 mm, and a globe having a maximum outer diameter limited in therange from 55 to 60 mm and attached to the cover with the arc tubeenclosed in the globe in such a manner that A2>A1>A3, wherein A1represents the minimum distance between the globe and each crown of thearc tube, A2 the minimum distance between the maximum diameter portionof the globe and the arc tube, and A3 the minimum distance between thebase end of the globe and the arc tube, the feature of the inventiondescribed above enables the determination of the optimum criteria forluminous intensity distribution in the direction of the sides and thecrown of the arc tube.

[0029] The above configuration increases the luminous intensitydistributed in the direction of the base and is therefore particularlyeffective in bringing the characteristics of luminous intensitydistribution of the lamp into close proximity to those of anincandescent lamp. As a result, the lamp can be illuminated as if itwere an incandescent lamp and used for a luminaire that is designed foran incandescent lamp without giving any disagreeability.

[0030] As the outer diameter of the globe or the diameter of the portionof the cover where the base is located has to be limited to no largerthan 45 mm in order to make the lamp resemble a typical light bulb andmore suitable to be fitted in a luminaire that uses a typical lightbulb, the upper limit of the maximum width of the arc tube along whichthe U-shaped bent bulbs are arranged is set at 43 mm, taking theclearance between the inner surface of the globe or the cover and theouter circumferential surface of the arc tube into consideration. Incases where a self-ballasted fluorescent lamp is installed in aluminaire designed for a typical light bulb, limiting the outer diameterof the globe or the diameter of the portion of the cover where the baseis located to no larger than 45 mm presents such other benefits asensuring a wide clearance between the lamp and the other components ofthe luminaire, thereby enabling the radiation under good conditions.

[0031] By setting A1 in the range from 2 to 8 mm, A2 in the range from 3to 13 mm and A3 in the range from 2 to 8 mm in the configuration of theself-ballasted fluorescent lamp described above, the optimum criteriafor distributing light toward the sides and the crown of the arc tubecan be determined.

[0032] By forming the self-ballasted fluorescent lamp described above soas to have an outer shape resembling a typical light bulb for generalillumination, the invention permits the lamp to be mounted in aluminaire designed for a typical light bulb, thereby expanding the rangeof usage. As the self-ballasted fluorescent lamp having an outer shaperesembling a typical light bulb can be mounted in such a luminairewithout giving any disagreeability, the invention is also capable ofimproving the appearance of the self-ballasted fluorescent lamp. Theterm ‘light bulb for general illumination’ mentioned above means a lightbulb defined as JIS Standard C 7501. In cases where a self-ballastedfluorescent lamp is provided with a globe, it is desirable that theshape of the outline of the globe be similar to the glass light bulb ofa typical light bulb.

[0033] As yet another feature of the invention, bonding the arc tube,the globe and the supporting member supporting the arc tube of aself-ballasted fluorescent lamp having the configuration as above to oneanother by means of a bonding agent permits the heat to be efficientlyradiated from the arc tube through the globe and also simplifies thestructure, thereby enabling the reduction of the production costs.

[0034] Furthermore, by arranging the U-shaped bent bulbs of the arc tubeof a self-ballasted fluorescent lamp having the configuration as abovein such a manner that their cross sections give the appearance of atriangle, the arc tube can be arranged in a compact shape.

[0035] By setting the distance w1 between the two straight portions ofeach U-shaped bent bulb of a self-ballasted fluorescent lamp having theconfiguration as above to be nearly identical to the distance w2 betweeneach straight portion of a U-shaped bent bulb and the U-shaped bent bulbthat is adjacent to said straight portion, and respectively limiting thedistances w1,w2 in the range from 1 to 5 mm, the arc tube can bearranged in a compact shape. Although the distances w1,w2 may be set atany desired dimensions on condition of being in the range from 1 to 5mm, it is desirable for production reasons that they be in the rangefrom 2 to 3 mm. Further, a distance that exceeds 5 mm may make itimpossible to produce a compact lamp.

[0036] According to yet another feature of the invention, the lightingcircuit of a self-ballasted fluorescent lamp having the configuration asabove includes a half-bridge type inverter main circuit having at leasta pair of transistors consisting of an N-channel transistor and aP-channel transistor, which are connected in series with each other toan input power supply and serve as the main switching element forgenerating a high frequency voltage; a ballast choke connected to theinverter main circuit so as to light the arc tube in stable conditions;and a control means which has a secondary winding magnetically connectedto the ballast choke and shared by the N-channel transistor and theP-channel transistor so that the control means serves to control thetransistors by means of the secondary winding. With the configuration asabove, wherein the control means operates the N-channel transistor andthe P-channel transistor, the invention enables the control of aplurality of transistors under different conditions based on output froma single control means, thereby simplifying the configuration of thecircuit. By using a lighting circuit which requires only a minimalnumber of parts as described above, the dimensions of the self-ballastedfluorescent lamp can be further reduced.

[0037] According to yet another feature of the invention, aself-ballasted fluorescent lamp includes an arc tube; a cover having abase; and a lighting circuit that has a circuit board and electricalcomponents mounted on both sides of the circuit board in such a mannerthat the circuit board is contained in the cover and faces the ends ofthe arc tube and that the electrical components mounted on the sidefacing the arc tube are so positioned as to not be aligned with the endsof the arc tube. By so positioning the circuit board as to face the endsof the arc tube and mounting electrical components on both sides of thecircuit board, the configuration described above is capable of reducingthe dimensions of the circuit board and, consequently, reducing thediameter of the portion of the lamp near the base. Furthermore, by soarranging electrical components mounted on the side facing the arc tubeas to not be aligned with the ends of the arc tube, the configuration iscapable of preventing interference of the arc tube with the electricalcomponents, limiting the influence of the heat from the arc tube, andreducing the length of the lamp.

[0038] According to yet another feature of the invention, aself-ballasted fluorescent lamp includes an arc tube; a cover having abase; and a lighting circuit and a lighting circuit that has a circuitboard and electrical components mounted on both sides of the circuitboard in such a manner that the circuit board is contained in the coverand faces the ends of the arc tube and that the electrical componentsmounted on the side facing the arc tube are so positioned as to not bealigned with the minute tubes of the arc tube. By so positioning thecircuit board as to face the ends of the arc tube and mountingelectrical components on both sides of the circuit board theconfiguration described above is capable of reducing the dimensions ofthe circuit board and, consequently, reducing the diameter of theportion near the base. Furthermore, by so arranging electricalcomponents mounted on the side facing the arc tube as to not be alignedwith the minute tubes of the arc tube, the configuration is capable ofpreventing interference of the minute tubes that project further fromthe arc tube with the electrical components, limiting the influence ofthe heat from the arc tube, and reducing the length of the lamp.

[0039] By forming a self-ballasted fluorescent lamp having theconfiguration described above in such a manner that the outer diameterof the circuit board is nearly identical to the inner diameter of thecover, the invention makes it possible to arrange components with thespace inside the cover used to the full extent and, consequently, reducethe diameter of the portion near the base.

[0040] In the configuration of a self-ballasted fluorescent lampdescribed above, by positioning the electrical components mounted on theside facing the arc tube apart from the electrodes of the arc tube, theinfluence that the heat generated by the electrodes exerts on theelectrical components can be limited.

[0041] A luminaire according to the invention is provided with aself-ballasted fluorescent lamp which has any one of the configurationsdescribed above. Using a compact self-ballasted fluorescent lampaccording to the invention enables the use of a luminaire designed for atypical light bulb. The invention also enables the reduction of thediameter of the portion of the self-ballasted fluorescent lamp near thebase and the length of the lamp, the use of a socket designed for anincandescent lamp without any disagreeability, the reduction ofproduction costs and the improvement of the appearance.

BRIEF DESCRIPTION OF DRAWINGS

[0042]FIG. 1 is a side view of a self-ballasted fluorescent lampaccording to a first embodiment of the present invention, wherein theglobe of the lamp is illustrated as if the inside contents were visible;

[0043]FIG. 2 is a bottom view of same, wherein the globe of the lamp isillustrated as if the inside contents were visible;

[0044]FIG. 3 is a sectional view of a part of said self-ballastedfluorescent lamp;

[0045]FIG. 4 is a side view of a U-shaped bent bulb of saidself-ballasted fluorescent lamp;

[0046]FIG. 5 is a sectional view of a part of said U-shaped bent bulb;

[0047]FIG. 6 is a graph showing the relationship among outer tubediameters of said U-shaped bent bulb, lamp efficiencies and maximumwidths of the arc tube;

[0048]FIG. 7 is a schematic illustration to explain the arrangement ofsaid U-shaped bent bulb;

[0049]FIG. 8 is a circuit diagram of a lighting circuit of said lamp;

[0050]FIG. 9 is a side view of a partially-cutaway self-ballastedfluorescent lamp according to a seventh embodiment of the presentinvention;

[0051]FIG. 10 is a side view of a partially-cutaway self-ballastedfluorescent lamp according to an eighth embodiment of the presentinvention;

[0052]FIG. 11 is a sectional view of a part of a partially-cutawayself-ballasted fluorescent lamp according to a ninth embodiment of thepresent invention;

[0053]FIG. 12 is a perspective of a part of said self-ballastedfluorescent lamp; and

[0054]FIG. 13 is a schematic illustration of said self-ballastedfluorescent lamp as viewed from the bottom. Furthermore,

[0055]FIG. 14 illustrates a fluorescent lamp according to a tenthembodiment of the present invention, wherein (a) is an exploded view ofa bulb of the fluorescent lamp, and (b) is an enlarged sectional view ofthe part A in FIG. 14 (a).

[0056]FIG. 15 is a side view of said fluorescent lamp;

[0057]FIG. 16 is a top view of same, wherein the globe of saidfluorescent lamp is illustrated as if the inside contents were visible;

[0058]FIG. 17 is a sectional view of a part of said fluorescent lamp;

[0059]FIG. 18 is an exploded view of a bulb of a fluorescent lampaccording to an 11th embodiment of the present invention;

[0060]FIG. 19 is a circuit diagram of a lighting circuit of saidfluorescent lamp; and

[0061]FIG. 20 is a top view of a fluorescent lamp according to a 12thembodiment of the present invention, wherein the globe of saidfluorescent lamp is illustrated as if the inside contents were visible.

BEST MODE FOR CARRYING OUT THE INVENTION

[0062] Next, a fluorescent lamp, a self-ballasted fluorescent lamp and aluminaire according to an embodiment of the present invention areexplained hereunder, referring to the drawings.

[0063] A first embodiment of the present invention is shown in FIGS. 1through 5, wherein FIG. 1 is a side view of the self-ballastedfluorescent lamp with the globe of the lamp illustrated as if the insidecontents were visible; FIG. 2 is a bottom view of same with the globe ofthe lamp illustrated as if the inside contents were visible; FIG. 3 is asectional view of a part of the self-ballasted fluorescent lamp; FIG. 4is a side view of a U-shaped bent bulb; and FIG. 5 is a sectional viewof a part of said U-shaped bent bulb.

[0064] Referring to FIGS. 1 through 3, numeral 10 denotes aself-ballasted fluorescent lamp, comprising a cover 14 having a base 12,a lighting circuit 16 contained in the cover 14, a translucent globe 17,and an arc tube 18 contained in the globe 17. The globe 17 and the cover14 form an envelope 19 that has such an outer shape as to have nearlythe same dimensions as standard dimensions of an electric light bulb forgeneral illumination, e.g. a 60W-type incandescent lamp. In other words,the height H1 of the envelope 19 ranges from approximately 110 to 125 mmincluding the base 12; the diameter D1, i.e. the outer diameter; and theouter diameter D2 of the cover 14 is approximately 40 mm. The term‘electric light bulb for general illumination’ mentioned above means alight bulb defined as JIS Standard C 7501. Further, in the explanationhereunder, the side where the base 12 is located is referred to as theupper side, while the side where the globe 17 is located is referred toas the lower side.

[0065] The cover 14 is provided with a cover body 21 that may be formedof a heat resistant synthetic resin such as polybutylene terephthalate(PBT). The cover body 21 has an approximately cylindrical shape thatflares downward. The base 12, which may be of the E26 type, is disposedover the top of the cover body 21 and fastened thereto with a bondingagent, or by such other means as crimping.

[0066] The globe 17 may be transparent or photo-diffusing milky white.The globe 17 is formed of glass, synthetic resin or the like into asmoothly curved shape nearly identical to the glass bulb of a typicallight bulb having a rated power consumption of approximately 60W. Theedge of the opening of the globe 17 is formed into a fitting edge 17 ato be fitted in an opening at the bottom of the cover 14. The luminanceof the lamp may be made more uniform by forming the globe 17 incombination with another member, such as a diffusion film.

[0067] As shown in FIGS. 1 and 3, the lighting circuit 16 contained inthe cover 14 has a disk-shaped circuit board 24 disposed horizontally,in other words perpendicularly to the lengthwise direction of the arctube 18. A plurality of electrical components 25,26 are respectivelymounted on both sides of the circuit board 24, i.e. the upside facingthe base 12 and the underside facing the arc tube 18, thereby forming aninverter circuit (a high-frequency lighting circuit) for conducting highfrequency lighting.

[0068] Of the of electrical components 25,26 mentioned above, theelectrical components 25 mainly consisting of components havingrelatively low heat resistance, such as electrolytic condensers and filmcondensers, are mounted on the upper face of the circuit board 24, whileelectrical components 26 consisting of thin, small chip-shapedrectifiers, rectifying devices or diode bridges having relatively highheat resistance, transistors, resistors, etc. that are arranged in apackage approximately 2 to 3 mm in thick are mounted on the underside ofthe circuit board 24.

[0069] The circuit board 24 has a shape resembling a disk whosediameter, i.e. the maximum width, ranges up to 1.2 times the maximumdimension along which the U-shaped bent bulbs are arranged. A total offour circuit-side wires 28 adapted to serve as the output unit arearranged in two pairs and drawn out of the circuit board 24. Instead ofproviding the circuit-side wires 28, wrapping pins may be set in thecircuit board 24.

[0070] As shown in FIGS. 1 through 5, the arc tube 18 contained in theglobe 17 consists of three U-shaped bent bulbs 31 that have nearlyidentical shapes and arranged at given locations. The three U-shapedbent bulbs 31 are connected to one another via communicating tubes 32 soas to form a single discharge path. Each U-shaped bent bulb 31 isprovided with a phosphor film, which is formed on the inner surface ofthe U-shaped bent bulb 31, and hermetically contained a rare gas, suchas argon, and mercury. Each U-shaped bent bulb 31 is a cylindrical bulbmade of glass having outer tube diameter d1 ranging from 8 to 11 mm, aninner tube diameter d2 ranging from 6 to 9 mm, a thickness of the tubewall ranging from 0.7 to 1.0 mm and a length ranging from approximately110 to 130 mm. Each U-shaped bent bulb 31 is formed into a smoothlycurved U-like shape having a crown P by bending said glass bulb at themiddle portion so that the bulb 31 has a bent portion 31 a that issmoothly turned back on itself and a pair of straight portions 31 bextending parallel to each other and integrally connected to the bentportion 31 a. The height H2 of the bulbs of the arc tube 18 formed asabove ranges from 50 to 60 mm; the length of the discharge path rangesfrom 200 to 300 mm; and the maximum width along which the bulbs arearranged, i.e. the dimension represented by D3 in FIG. 1, ranges from 32to 43 mm.

[0071] The arc tube 18 is fastened to a partition plate 33, which may bereferred to as a supporting member in the claims or other parts of thespecification and serves as a fluorescent lamp fastening member as wellas a lighting circuit fastening member. The partition plate 33 isfastened to the cover 14. To be more specific, the partition plate 33has a disk-shaped base portion 34 which is provided with mounting holes34 a. The arc tube 18 is fastened to the partition plate 33 with theends of the U-shaped bent bulbs 31 respectively inserted into themounting holes 34 a and secured therein by means of, for example,bonding the regions of the bulbs to the base portion with an adhesiveagent. A fitting step portion 35 that extends upward and then outward isformed around the outer edge of the base portion 34. These members arefastened to one another by fitting the fitting step portion 35 in thecover 14 and filing the gap between the fitting step portion 35 and thecover 14 with a bonding agent 37 in such a state that the fitting edge17 a of the globe 17 is fitted between the fitting step portion 35 andthe cover 14. A mounting edge 38 that may have a cylindrical shape risesfrom the top of the fitting step portion 35, and the circuit board 24 ofthe lighting circuit 16 is fitted, bonded or otherwise attached to themounting edge 38.

[0072] When the self-ballasted fluorescent lamp 10 is assembled in themanner described above, the arc tube 18 is housed in the globe 17 at agiven position. To be more specific, in the state where theself-ballasted fluorescent lamp 10 is assembled, the crowns P of theU-shaped bent bulbs 31 are aligned at regular intervals in a circlewhose center is on the central axis of the self-ballasted fluorescentlamp 10 extending in the vertical direction, and the straight portions31 b of the U-shaped bent bulbs 31, too, are aligned at regularintervals in a circle whose center corresponds to the central axis ofthe lamp. In other words, as shown in FIG. 7, the tube axes of thestraight portions 31 b of the three U-shaped bent bulbs 31 arerespectively located at the approximate vertexes of a regular hexagon.The distance w1 between the two straight portions 31 b of each U-shapedbent bulb 31 is nearly identical to the distance w2 between eachstraight portion 31 b and the U-shaped bent bulb 31 adjacent to saidstraight portion 31 b, and the distances w1,w2 are in the range between1 mm and 5 mm. Although the distances w1,w2 may be set at any desiredvalues on condition of being in the range from 1 to 5 mm, it isdesirable for production reasons that they are in the range between 2 mmand 3 mm. Further, a distance that exceeds 5 mm may make it impossibleto produce a compact lamp.

[0073] Referring to FIGS. 6 and 7, the reason for setting the maximumwidth a of the aforementioned arc tube 18 in the range from the 32 to 43mm and the outer tube diameter d1 of each U-shaped bent bulb 31 in therange from 8 to 11 mm is explained hereunder.

[0074]FIG. 6 shows the lamp efficiency in the case where the thicknessof the tube wall of the arc tube 18, the gas pressure, the length of thedischarge path and the lamp current are respectively set at 0.8 mm, 400Pa, 250 mm and 0.2 A, and also shows the relationship between themaximum width a and the outer tube diameter d1 of each U-shaped bentbulb 31 regarding the exemplary configurations where the distances w arerespectively 5 mm and 2 mm.

[0075] In order to make the lamp resemble a typical light bulb and moresuitable to be fitted in a luminaire that uses a typical light bulb, theouter diameter of the glove 17 has to be 45 mm or less (around 40 mmbeing most desirable). In case of the present embodiment, the upperlimit of the maximum width a df the arc tube 18 is set at 43 mm, takingthe clearance between the inner surface of the globe 17 or the cover 14and the outer circumferential surface of the arc tube 18 intoconsideration.

[0076] The lower limit of the outer tube diameter d1 is set at 8 mm,where the relative lamp efficiency becomes 97% or more.

[0077] The upper limit of the outer tube diameter d1 is determined basedon the equation a=3d1+2w, wherein the upper limit of the maximum width aof the arc tube 18 is 43 mm. It has to be noted that the tube axes ofthe straight portions 31 b of the three U-shaped bent bulbs 31 of thearc tube 18 are respectively located at the approximate vertexes of aregular hexagon. In other words, w1 and w2 are nearly equal. Therefore,the upper limit of the outer tube diameter d1 is set at 11 mm byreplacing the variables in the equation a=3d1+2w with the maximumdimensions, in other words by replacing ‘a’ and ‘w’ with 43 and 5respectively, and finding the value of d1 from the equation 43=3d1+2×5.

[0078] The lower limit of the maximum width a of the arc tube 18 is setat 28 mm by replacing the variables in the equation a=3d1+2w with theminimum dimensions, in other words by replacing “d1” and “w” with 8 and2 respectively, and finding the value of a from the equation a

[0079] The lower limit of the inner tube diameter is set at 6 mm,because the inner tube diameter of less than 6 mm would result in anexcessively high starting voltage and therefore be notpractical.=3×8+2×2.

[0080] Should the thickness of the tube wall be 1.1 mm or more, theglass material tends to accumulate at the inside of the U-shaped curvedportions 31 a, making such portions prone to cracks. Such anaccumulation of glass can be limited by setting the thickness of thetube wall to be in the range between 0.7 mm and 1.0 mm. Given that theminimum clearance between the globe 17 and each crown P of the arc tube18 is A1; the minimum clearance between the portion where the outerdiameter of the globe 17 is the greatest and the arc tube 18 is A2; andthat the minimum clearance between the base end of the globe 17 and thearc tube 18 is A3, the relationship among them has to be as shown in therepresentation: A2>A1≧A3, wherein A1, A2 and A3 are respectively in theranges from approximately 2 to 8 mm, from approximately 3 to 13 mm andfrom approximately 2 to 8 mm. By setting the relative dimensions such asA2>A1≦A3, the distribution of luminous intensity can be made such thatthe light distributed to the crowns is more intense. Furthermore, bysetting A1 such as A2>A1=A3, i.e. 2 mm>A1≧>8 mm, the light distributedto the crowns can be further intensified, in other words the optimumcriteria for luminous intensity distribution to the side wall and thecrown of the arc tube 18 can be obtained. Using a luminance meter (BM-8manufactured by TOPCON CORP.), the surface luminance of the globe 17 wasmeasured to be 380 cd/m². Results of the experiment also indicated thatthe total light flux amounted to be 810 lm.

[0081] One of the two ends of each U-shaped bent bulb 31 is sealed bymeans of a line seal with a mount, a pinch seal without a mount, or thelike. A minute tube 41 that may otherwise be called an exhaust tube iswelded to the other end of each U-shaped bent bulb 31 to discharge theair. The minute tube 41 is designed such that it may be provided with anamalgam 42 if it is necessary. A filament coil 44 is disposed at the endof each U-shaped bent bulb 31 that is located at an end of the arc tube18 in such a state that each filament coil 44 is supported between apair of copper-weld wires (lead-in wires) 45 by use of a line seal witha mount or the like. Via each respective dumet wire 46 attached to theglass at the end of the U-shaped bent bulb 31 and thus sealed in thebulb, each copper-weld wire 45 is connected to a lamp wire 48 that isdrawn out of the U-shaped bent bulb 31. If it is necessary, one of thecopper-weld wires 45 may be provided with an auxiliary amalgam 49.

[0082] As shown in FIG. 3, the four lamp wires 48 that are arranged intwo pairs and drawn out of the arc tube 18 are electrically andmechanically connected to the lighting circuit 16 as they are twistedwith circuit wires 28 that are drawn from the lighting circuit 16. Eachset of wires 28,48 are inserted into a groove formed in the rib-likemounting edge 38 of the partition plate 33, and thus guided by thegroove. Compared with a structure that calls for providing the lightingcircuit 16 with a connector and inserting the lamp wires 48 into theconnector to electrically connect the wires to the lighting circuit 16,or another structure that calls for electrically connecting the lampwires 48 by wrapping the wires around column-shaped pins that areprojected from the lighting circuit 16, the configuration according tothe embodiment described above requires only a limited space andtherefore is capable of reducing the dimensions of the lamp.Furthermore, as there is no need of parts dedicated for the connection,the embodiment also ensures easy, reliable connection of wires at a lowcost. Should there be a great difference between the diameters of eachcircuit wire 28 and lamp wire 48, such a difference makes a twistingoperation difficult. Therefore, it is desirable to set the relativedimensions of the wires, i.e. the diameter D28 of each circuit wire 28and the diameter D48 of each lamp wire 48, to be (0.9×D28)<D48<(1.1×D28)to ensure easy and reliable connection. The electrical and mechanicalconnection of the wires can be made even more reliable by twisting thewires no fewer than three turns. In an alternative configuration whereinmembers in the shape of a cylindrical pin are projected upward from thepartition plate 33, each pair of wires 28,48 may be connected bytwisting around one of these cylindrical members.

[0083] In cases where the inner tube diameter d3 of the minute tube 41of each U-shaped bent bulb for discharging gas from the U-shaped bentbulb is too small with respect to the inner tube diameter d2 of theU-shaped bent bulb 31, it is necessary to increase the duration of gasdischarge due to the poor exhaust efficiency. In cases where the minutetube 41 has an excessively large diameter, it is impossible to provide asufficient clearance between the outer surface of the minute tube 41 orthe inner surface of the U-shaped bent bulb 31 and each copper-weld wire45, which is attached to and sealed in the bulb at the same time whenthe minute tube 41 is attached. Such a lack of a sufficient clearancetends to cause an improper attachment or other problems, often degradingthe quality of the arc tube 18. A U-shaped bent bulb of a conventionallamp, in particular, has an inner tube diameter more than three times aslarge as the inner tube diameter of its minute tube 41, making itdifficult to improve the air discharge efficiency, because the minutetube 41 for discharging the air is disposed at one of the lengthwiseends of the arc tube in many cases. In order to solve this problem, thepresent embodiment calls for setting the inner tube diameter d3 of eachminute tube 41, with respect to the inner tube diameter d2 of theU-shaped bent bulb 31, to be within the range 2.0<(d2/d3)<2.8. Thusincreasing the inner tube diameter d3 of the minute tubes 41 improvesthe quality of the arc tube 18 by increasing the air dischargeefficiency as well as ensuring the reliable sealing and attachment ofthe minute tubes 41. Furthermore, the minute tubes 41 serving as exhaustpipes may be disposed about the middle of the length of the arc tube 18to increase the air discharge efficiency.

[0084] The self-ballasted fluorescent lamp 10 structured as above hassuch characteristics that, when a rated input power is 14W, a highfrequency power of 12.5 W is applied to the arc tube 18, producing alamp current of 280 mA, a lamp voltage of 65 V and a total luminous fluxof 810 lm, which results from the use of the three band phosphor.

[0085]FIG. 8 is a circuit diagram illustrating the configuration of thelighting circuit 16. The lighting circuit 16 has an input power unit E.The input power unit E includes a condenser C1 which constitutes afilter and is connected to a commercial AC power supply e via a fuse F1,and a full-wave rectifying circuit 51 whose input terminal is connectedto the condenser C1 via an inductor L1 that constitutes a filter. Asmoothing condenser C2 is connected to the output terminal of thefull-wave rectifying circuit 51 via a resistor R1, and an inverter maincircuit 52 of a half-bridge type is connected to the condenser C2.

[0086] The inverter main circuit 52 comprises a series circuit of fieldeffect transistors Q1,Q2 serving as a switching element is connected inparallel with the condenser C2. The field effect transistor Q1 is anN-channel transistor of the MOS type, while the field effect transistorQ2 is a P-channel transistor of the MOS type. The source of theN-channel field effect transistor Q1 and the source of the P-channelfield effect transistor Q2 are connected to each other.

[0087] An end of each one of the filament coils 44,44, which arerespectively disposed at the two ends of the arc tube 18, is connectedto a point between the drain and the source of the field effecttransistor Q2 via a ballast choke L2 and a condenser C3 for interruptingdirect current. In case of the present embodiment, the ballast choke Ualso serves to generate resonance. A start-up condenser C4 is disposedbetween and connected to the aforementioned one end of the one of thefilament coils 44,44 and the other end of the other filament coil 44. Anactivating resistor R2 which forms a part of an activating circuit 53 isconnected to the gate of the field effect transistor Q1, the gate of thefield effect transistor Q2, and the junction point where the resistor R1and the condenser C2 are connected. A series circuit of a condenser C5and a condenser C6 is disposed between and connected to the gates of thefield effect transistors Q1,Q2 and the sources of the field effecttransistors Q1,Q2. A series circuit which consists of a Zener diode ZD1and a Zener diode ZD2 and serves to protect the gates of the fieldeffect transistors Q1,Q2 is connected in parallel with a series circuitconsisting of the condenser C5 and the condenser C6. The condenser C6forms a part of a control circuit 54 that serves as a control means. Theballast choke L2 is provided with a secondary winding L3, which ismagnetically joined to the ballast choke L2 and connected to a resonancecircuit 56 that consists of an inductor L4 and the condenser C6.Furthermore, a resistor R3 of the activating circuit 53 is connected inparallel to a series circuit consisting of the condenser C5 and theinductor L4.

[0088] A parallel circuit consisting of a resistor R4 of the activatingcircuit 53 and a condenser C7 is disposed between and connected to thedrain and the source of the field effect transistor Q2. Said condenserC7 serves to improve the switching function.

[0089] The field effect transistors Q1,Q2 may be of a bipolar type. Theinverter main circuit 52 may have two or more pairs of seriallyconnected switching elements. One of the examples of such aconfiguration is a full-bridge type. Furthermore, it does not matterwhether the arc tube 18 is of a type which calls for preheating bothfilament coils 44 or a type wherein neither filament coil 44 ispreheated.

[0090] With the configuration as above, when the power is fed into thelighting circuit 16, the voltage on the commercial AC power supply e isrectified over the full wave by the full-wave rectifying circuit 51 andsmoothed by the condenser C2.

[0091] The voltage is applied through the resistor R2 to the gate of theN-channel field effect transistor Q1, thereby turning on the fieldeffect transistor Q1. As a result, a voltage is applied to the circuitconsisting of the ballast choke L2, the condenser C3 and the condenserC4 so that the bast choke L12 and the condenser C4 generate resonance.As a voltage is induced on the secondary winding L3 of the ballast chokeL2, intrinsic resonance between the inductor LA and the condenser C6 ofthe control circuit 54 is generated, thereby generating such a voltageas to turn on the field effect transistor Q1 and turn off the fieldeffect transistor Q2. When the resonance voltage between the ballastchoke L2 and the condenser C4 is inverted thereafter, a voltage which isthe reverse of the aforementioned voltage is generated on the secondarywinding L3 so that the control circuit 54 generates such a voltage as toturn off the field effect transistor Q1 and turn on the field effecttransistor Q2. Then, when the resonance voltage between the ballastchoke L2 and the condenser C4 is inverted, the field effect transistorQ1 is turned on, while the field effect transistor Q2 is turned off.Thereafter, the field effect transistor Q1 and the field effecttransistor Q2 are alternately turned on and off in the same manner asabove to generate resonance voltage so that a starting voltage isapplied to the arc tube 18 that is connected in parallel with thecondenser C4, while one of the filament coils 44 is preheated. Thus, thearc tube 18 is started and becomes illuminated.

[0092] The Zener diode ZD1 and the Zener diode ZD2 unify the voltages onthe gates of the field effect transistor Q1 and the field effecttransistor Q2 and also protect the gates from an excessively highvoltage.

[0093] Therefore, by using the N-channel field effect transistor Q1 andthe P-channel field effect transistor Q2 and connecting the N-channelfield effect transistor Q1 to the side where the electric potential ishigher, both the N-channel field effect transistor Q1 and P-channelfield effect transistor Q2 can be controlled by a single controlcircuit, i.e. the control circuit 54. As the control circuit 54 isprovided with a resonance circuit consisting of the inductor LA and thecondenser C6, the size of the control circuit 54 can be reduced byreducing the number of the turns of the secondary winding L3, and it isalso possible to reduce the difference between the voltage output fromthe control circuit 54 when no load is applied and the voltage outputfrom the control circuit 54 under a load. If the resonance circuitconsisting of the inductor LA and the condenser C6 is omitted so thatthe output voltage from the secondary winding L3 is directly output,there may be a more than 10-fold difference in voltage output from thesecondary winding 13 during no-load period and voltage output duringon-load period. Although the magnitude of the difference depends on therelationship between the start-up voltage and the lamp voltage on thearc tube 18, such a large difference may either make it difficult forZener diodes to perform unification of the gate voltages and protectionof the gates or require expensive kinds of Zener diodes.

[0094] The present embodiment includes an arc tube 18 comprised of aplurality of U-shaped bent bulbs 31 having an inner tube diameter of 6to 9 mm and arranged in parallel to one another in such a way that theheight H2 of the bulb ranges from 50 to 60 mm; the length of thedischarge path ranges from 200 to 300 mm; and that the total luminousflux is 700 lm when the lamp is lit at the lamp power of 7 to 15 W. Bylimiting the height H1 of the envelope 19 that is provided with thecover 14 within the range from 110 to 125 mm including the height of thebase 12, to which said arc tube 18 is attached, the optimum criteria forthe components can be determined in order to make the dimensions and thetotal luminous flux of the lamp correspond to those of a typical,60W-type light bulb for general illumination. The lower limit of theinner tube diameter of the tube is set at 6 mm as mentioned above,because the tube having an inner tube diameter of less than 6 mmrequires a considerably high starting voltage and is thereforeimpractical.

[0095] As the embodiment includes an arc tube 18 comprised of aparallely arranged plurality of U-shaped bent bulbs 31, each of whichhas an outer tube diameter of 8 to 11 mm, a bulb wall from 0.7 to 1.0 mmthick and a curved crown P, it is possible to determine the tubediameter so that the dimensions and the total luminous flux of the lampcorrespond to those of a typical, 60W-type light bulb for generalillumination and also determine the range of the thickness of the bulbwall which enables the increase of the inner surface area of the bulbwhile ensuring sufficient strength within the limit of the outerdiameter of the bulb determined as above. Should the bulb wall have athickness of 1.1 mm or more, the inner diameter of the bulb becomes toosmall with respect to the outer diameter of the bulb. Not only does thismake it impossible to increase the inner surface area but also causesglass to accumulate in the bent portion 31 a, at which each glass bulbis bent into a U-like shape. Such an accumulation of the glass makes theinner face of the bent portion 31 a prone to cracks. By limiting thebulb wall thickness within the range from 0.7 to 1.0 mm, however, theembodiment is capable of reducing the danger of glass accumulatinginside each bent portion 31 a.

[0096] The maximum width of the circuit board 24 is so set as to rangeup to 1.2 times the maximum dimension along which the U-shaped bentbulbs 31 of the arc tube 18 are arranged, and the electrical components26 that have relatively high heat resistance are mounted on one side ofthe circuit board 24, i.e. the side facing the arc tube 18, while theelectrical components 25 having relatively low heat resistance aremounted on the other side of the circuit board 24. Thus, the embodimentis capable of reducing the size of the circuit board 24 while limitingthe influence that heat exerts on the electrical components 25,26mounted on the circuit board 24. Consequently, the embodiment is capableof reducing the dimensions of the cover 14, which contains the circuitboard 24 to a level equivalent to the dimensions of a typical lightbulb. The influence that the heat from the electrodes exerts on theelectrical components 26 can be limited by positioning the electricalcomponents 26 apart from the electrodes of the arc tube 18 when theelectrical components 26 are mounted on the side of the circuit board 24facing the arc tube 18. Although it is recommended that the circuitboard 24 have a circular shape, which is the most effective shape toensure the space for mounting, the circuit board 24 may have a polygonalshape, such as a square, or an oval shape.

[0097] The arc tube 18 comprises three or more U-shaped bent bulbs 31,each of which has a smoothly bent crown P. These U-shaped bent bulbs 31are serially connected to one another and concentrically arranged insuch a manner that their crowns P are aligned in a circle and face theinner surface of the globe 17 and that the U-shaped bent bulbs 31 arespaced apart at a distance not exceeding the outer diameter of eachbulb. Thus, this configuration makes it possible to dispose the arc tube18 in the globe 17 that is formed in a compact shape resembling atypical light bulb. This embodiment is also capable of providing moreuniform luminosity and more effective illumination even if the arc tube18 is contained in such a compact globe 17.

[0098] As the arc tube 18 can be produced simply by forming threeU-shaped bent bulbs 31 having an essentially identical shape andconnecting them together, without the need of bending a glass tube intoa complicated shape, the present embodiment is capable of reducing theproduction costs.

[0099] According to the configuration of the embodiment, the globe 17includes an arc tube 18 comprised of a plurality of U-shaped bent bulbs31 having an outer bulb diameter ranging from 8 to 11 mm and arrangedparallel to one another in such a manner that the maximum width of thearc tube 18, i.e. the dimension along which the U-shaped bent bulbs 31are arranged ranges from 32 to 43 mm. Furthermore, the maximum outerdiameter of the globe 17 is in the range from 55 to 60 mm, and the globe17 encloses the arc tube 18 in such a manner that A2>A1≧A3, wherein A1represents the minimum distance between the globe 17 and each crown P ofthe arc tube 18; A2 represents the minimum distance between the maximumdiameter portion of the globe 17 and the arc tube 18; and A3 representsthe minimum distance between the base end of the globe 17 and the arctube 18. Therefore, the embodiment is capable of determining the optimumcriteria for luminance intensity distributing in the directions of thesides and the front end of the arc tube 18. Based on the aboveinequality, the optimum criteria for luminance intensity distributing inthe directions of the sides and the front end of the arc tube 18 can beprovided by setting A1 in the range from 2 to 8 mm, A2 in the range from3 to 13 mm and A3 in the range from 2 to 8 mm.

[0100] In case, for example, a self-ballasted fluorescent lamp accordingto the present embodiment is used for a ceiling-recessed type downlight, a large portion of the light is distributed toward the base. Inother words, the characteristics of luminous intensity distribution ofthe lamp are similar to those of an incandescent lamp so that thereflector disposed in the luminaire achieves the designed opticaleffect, with the light effectively radiated to the reflector, which islocated near the socket. In case the lamp is used for a table lamp or asimilar luminaire which is designed to project the image of the internallight source onto a photo-diffusing shade, which may be made of cloth,setting the lamp so as to have luminous intensity distributioncharacteristics similar to those of an incandescent lamp enables thelamp to be used without any disagreeability.

[0101] Bonding the supporting member, the arc tube and the globe to oneanother by means of a bonding agent permits the heat to be efficientlyradiated from the arc tube through the globe and also simplifies thestructure, thereby enabling the reduction of the production costs.

[0102] Furthermore, the arc tube 18 is formed in a compact shape withits U-shaped bent bulbs 31 arranged in such a manner that their crosssections give the appearance of a triangle.

[0103] The distance w1 between the two straight portions 31 b of eachU-shaped bent bulb 31 is nearly identical to the distance w2 betweeneach straight portion 31 b and the U-shaped bent bulb 31 adjacent tosaid straight portion 31 b, and the distances w1,w2 are in the rangebetween 1 mm and 5 mm. Therefore, the arc tube 18 is disposed in acompact configuration.

[0104] Through the control circuit 54, the lighting circuit 16 operatesthe N-channel field effect transistor Q1 and the P-channel field effecttransistor Q2. As the output from a single control circuit 54 thuscontrols two field effect transistor s in different conditions, theconfiguration of the circuit is simplified. By using a lighting circuit16 which, as described above, requires only a minimal number of parts,the dimensions of the self-ballasted fluorescent lamp 10 can be furtherreduced.

[0105] As a lamp according to the embodiment has an outer shaperesembling a typical light bulb having a rated power of approximately 60W, it can be mounted on a luminaire designed for a typical light bulb.Thus, the embodiment expands the range of usage and also improves theappearance, permitting the lamp to be used without giving anydisagreeability.

[0106] As shown in FIG. 3, the embodiment described above calls forsecuring the fitting edge 17 a of the globe 17 by injecting a bondingagent 37 into the groove that is formed between the fitting step portion35 and the cover 14. However, these parts may be affixed by usingvarious means.

[0107] For example, a groove open at the bottom may be formed along theouter circumferential edge of the partition plate 33 that secures thearc tube 18 so that the globe 17 may be secured by fitting the fittingedge 17 a of the globe 17 in this groove and injecting a bonding agent37, such as a silicon-based bonding agent, into the groove. In analternative configuration, the cover 14 and the partition plate 33 mayrespectively be provided with a catching portion and a catching portionreceiver so that the cover 14 and the partition plate 33 can be securedby engaging the catching portion of the cover 14 and the catchingportion receiver of the partition plate 33 with each other. Thisengagement of the partition plate 33 and the cover 14 can be done byinserting the partition plate 33 into the cover 14, or inserting thepartition plate 33 into the cover 14 and then rotating the partitionplate 33 in a given direction. According to this configuration, whereinthe globe 17 is fastened only to the partition plate 33, the membersforming the arc tube 18 and the components of the lighting circuit 16can be separated and recovered more easily compared with theconfiguration which calls for attaching the arc tube 18 and the lightingcircuit 16 to the partition plate 33 and fixing the globe 17 in thestate where the cover 14 is attached to the partition plate 33. Theabove configuration has such other benefits that it improves theappearance of the lamp by simplifying the structure of the componentsexposed to the outside and that it is applicable to a luminaire of othertypes, e.g. a luminaire which does not use a globe 17.

[0108] As an alternative way to fix the globe 17, a notch or a groovemay be formed in the partition plate 33, in the fitting step portion 35or other location near the globe 17 and the arc tube 18, so that thecover 14, the globe 17, the partition plate 33 and the arc tube 18 mayintegrally be bonded together by introducing a bonding agent 37, such asa silicon type bonding agent, into this notch or the groove, therebybonding the cover 14, the globe 17 and the partition plate 33 to oneanother. This configuration is capable of reducing the production costs,because its structure and production process are simpler than theconfiguration which calls for bonding the cover 14, the globe 17 and thepartition plate 33 together and bonding the arc tube 18 to the partitionplate 33 in a separate production process. In addition, it is capable offastening the arc tube 18 to the globe 17 more securely. Furthermore,because the above configuration permits the heat to be conducted fromthe arc tube 18 through the bonding agent 37 to the globe 17 andefficiently radiated through the globe 17, it is capable of limitingdeterioration of the luminous flux as well as increase in thetemperature of the lighting circuit 16 and, consequently, capable ofincreasing the reliability of the circuit.

[0109] Although the lighting circuit 16 according to the embodimentdescribed above is disposed in such a manner that a single circuit board24 is positioned horizontally, in other words perpendicularly to thedirection in which the base 12 is inserted, it does not matter whether aplurality of circuit boards are provided or the circuit board(s) arepositioned perpendicularly, i.e. in parallel to the direction in whichthe base 12 is inserted.

[0110] The lighting circuit 16 may be composed by arranging a firstcircuit board and a second circuit board in such a manner that bothcircuit boards extend horizontally one above the other. In thisembodiment, the upper first circuit board has electrical components 25mounted thereon, while electrical components 25 are-mounted on theunderside of the second circuit board located at the lower side, and thefirst and second circuit boards are arranged with their soldered sidesfacing each other. The electrical components 25 consisting of componentshaving relatively low heat resistance, such as electrolytic condensersor film condensers, are mounted on the first circuit board disposed atthe side where the base 12 is located, while electrical components 25, alarge part of which consists of those having relatively high heatresistance and having little thickness, such as resistors or chipcomponents for rectification, are mounted on the second circuit board.The first and second circuit boards are electrically connected via aplurality of jumper wires, which may be two or three tinned wires, orflexible, film-like cables. When the first circuit board and the secondcircuit board are incorporated in the lamp, the mounting of thesecircuit boards is done by bending the jumper lines in such a manner thatthe soldered sides of these two circuit boards face each other. Disposedbetween the soldered sides of the first and second circuit boards is aninsulating sheet which is approximately 1 mm thick and made of aninsulating, heat-resistant material having an excellent heat insulatingcapability, such as a silicon-type film or the like. Thus, the solderedsides are insulated from each other, and conduction of heat from the arctube 18 to the first circuit board is limited. By dividing the circuitcomponents into two circuit boards, the planar dimensions of thelighting circuit 16 is reduced. By thus making the circuit mountingstructure compact, the above configuration provides a lamp having ashape nearly identical to that of a typical light bulb. Dividing thecircuit components into two circuit boards has such other benefits as toenable the easy protection of electrical components 25 having low heatresistance and improve the reliability and facilitates mass-productionof the lamp.

[0111] In the configuration described above, components having low heatresistance, such as film condensers, and ballast chokes that generate agreat amount of heat may undergo what is generally called ‘siliconpotting’, i.e. a treatment which calls for placing silicon-based bondingagent on these components. Or a silicon-based resin rubber may bedisposed in the space provided between the second circuit board and thepartition plate 33 and filled with air. As thus using silicon potting orresin rubber enhances the outgoing radiation of heat from the electricalcomponents 25 and makes it difficult for the heat from the arc tube 18to be conducted to the electrical components 25, the temperature of theelectrical components 25 can be reduced.

[0112] Although the configuration described above calls for sealing theends of the arc tube 18 by means of line sealing using a mount, they maybe sealed by means of pinch sealing that does not use a mount so thatproduction costs can be reduced by excluding the process for producingmounts.

[0113] In an alternative configuration, the ends of the arc tube 18 maybe sealed by means of pinching that uses a jig. In case of aconventional configuration, supporting the filament coils 44 istypically done by clamping each filament coil 44 with a pair ofcopper-weld wires 45 fixed to a bead glass (a mount bead). Therefore,depending on the position or inclination of each bead glass, pinchingwith a jig presents the danger of damaging the phosphor film applied tothe inner surface of the arc tube 18 and consequently degrading thequality of the arc tube 18. According to the present embodiment,however, a mount used at each of the hot cathode fluorescent lamppermits the corresponding filament coil 44 to be directly clamped by twocopper-weld wires 45, and each clamping width is limited to 7 mm orless. By thus eliminating the need of sophisticated control of thepositions and inclinations of the bead glass, which control is essentialin cases where bead glasses are used, the present embodiment simplifiesthe production process of the arc tube 18, thereby reducing itsproduction costs, and also improves the quality of the arc tube 18. Incase of the present embodiment, too, the copper-weld wires 45 at oneside or the other are provided with an auxiliary amalgam 49.

[0114] Conventionally, sealing by pinching is done by directly pinchingthe dumet wires 46 of the copper-weld wires 45 with the arc tube 18 toseal the dumet wires 46 in the arc tube 18. As setting appropriateheating criteria, such as duration, temperature, etc. to securely bondthe metal dumet wires 46 and the glass act tube 18 is difficult andrequires sophisticated production technology, the conventional method ofpinching described above not only makes the reduction of productioncosts difficult but also presents a problem in that the occurrence ofany improper sealing would degrade the quality of the arc tube 18. Oneof the solutions to such problems is welding the glass to the dumetwires 46, i.e. the dumet portions, of the copper-weld wires 45beforehand and then attaching the dumet wires 46 to the arc tube 18 andthus sealing them in the arc tube 18 by pinching. Doing so facilitatesthe sealing of the arc tube 18, thereby improving the quality of the arctube 18, increasing the yield and reducing production costs.Furthermore, in the above configuration, bead glass, each of which isadapted to support two copper-weld wires 45, may be used.

[0115] According to the embodiment described above, a self-ballastedfluorescent lamp is provided with a globe 17 whose shape is similar tothe glass bulb of a typical light bulb having a rated power consumptionof approximately 60 W. However, the shape of the globe 17 is not limitedto the glass light bulb of a typical light bulb, and various shapes areapplicable. Furthermore, a configuration which does not have a globe 17is also applicable.

[0116]FIG. 9 is a side view of a partially-cutaway self-ballastedfluorescent lamp according to a seventh embodiment of the presentinvention, and FIG. 10 is a side view of a partially-cutawayself-ballasted fluorescent lamp according to an eighth embodiment of thepresent invention.

[0117] In the embodiment shown in FIG. 9, the arc tube 18 is exposedfrom the cover 14, because a globe 17 is not provided. Thisconfiguration provides a self-ballasted fluorescent lamp which is evenmore compact, more suitable to be used for a luminaire that uses atypical light bulb, and improves the total luminous flux characteristic.

[0118] By forming a globe 17 in the shape of a ball, the embodimentshown in FIG. 10 is capable of providing a globe 17 whose shaperesembles a ball-type glass bulb of a typical light bulb.

[0119] Although each one of the embodiments described above uses a milkywhite globe 17, a transparent globe, i.e. a clear-type globe, may beused.

[0120] A luminaire may be formed by attaching a self-ballastedfluorescent lamp 10 according to any one of the embodiments describedabove to the main body of a luminaire which is provided with a socketdesigned for a typical light bulb for general illumination. As a result,a luminaire having benefits described above, such as having more uniformluminance, being capable of improving the illumination efficiency andreducing production costs, can be provided.

[0121] According to each embodiment described above, an arc tube 18 isformed by connecting three U-shaped bent bulbs 31. However, the shape ofthe arc tube 18 is not limited to such a configuration; the lamp lengthmay be reduced by arranging a plurality of U-shaped or H-shaped bentbulbs, e.g. two, three or four bulbs, in parallel with one another so asto form a discharge path having four, six or eight axes extending in thelengthwise direction of the lamp.

[0122] Next, a self-ballasted fluorescent lamp and a luminaire accordingto the ninth embodiment of the invention are explained hereunder,referring to drawings.

[0123]FIG. 11 is a sectional view of a part of a self-ballastedfluorescent lamp according to an embodiment of the present invention;FIG. 12 is a perspective of a part of said self-ballasted fluorescentlamp; and FIG. 13 is a schematic illustration of the self-ballastedfluorescent lamp as viewed from the bottom.

[0124] The self-ballasted fluorescent lamp according to the ninthembodiment has the same appearance as that of the lamp shown in FIG. 1.

[0125] In FIGS. 11 through 13, numeral 10 denotes a self-ballastedfluorescent lamp. The self-ballasted fluorescent lamp comprises a cover14 having a base 12, a lighting circuit 16 contained in the cover 14, atranslucent globe 17, and an arc tube 18 contained in the globe 17. Theglobe 17 and the cover 14 together form an envelope 19 that has such anouter shape as to have nearly the same dimensions as standard dimensionsof an incandescent lamp having a rated power of approximately 60 W. Inother words, the lamp length H1 of the envelope 19 ranges fromapproximately 120 to 125 mm including the base 12; the diameter D1 ofthe envelope 19, i.e. the outer diameter of the globe 17, isapproximately 60 mm; and the maximum diameter D2 of the cover 14 isapproximately 40 mm. Further, in the explanation hereunder, the sidewhere the base 12 is located is referred to as the upper side, while theside where the globe 17 is located is referred to as the lower side.

[0126] The cover 14 is provided with a cover body 21 that may be formedof a heat resistant synthetic resin such as polybutylene terephthalate(PBT). The cover body 21 has an approximately cylindrical shape thatflares downward. The base 12, which may be of the E26 Edison type, isdisposed over the top of the cover body 21 and fastened thereto with abonding agent, or by such other means as crimping.

[0127] The globe 17 may be transparent or photo-diffusing milky white.The globe 17 is formed of glass, synthetic resin or the like into asmoothly curved shape that is nearly identical to the glass bulb of anincandescent lamp. The edge of the opening of the globe 17 is formedinto a fitting edge 17 a to be fitted in an opening at the bottom of thecover 14. The globe 17 may be formed in combination with another member,such as a diffusion film, in order to make luminance of the lamp moreuniform, or the globe 17 may entirely be omitted.

[0128] The lighting circuit 16 contained in the cover 14 has a circuitboard (a PC board) 24 disposed horizontally, in other wordsperpendicularly to the lengthwise direction of the arc tube 18. Aplurality of electrical components 25,26 are mounted on both sides ofthe circuit board 24, i.e. the upside facing the base 12 and theunderside facing the arc tube 18, thereby forming an inverter circuit (ahigh-frequency lighting circuit) for conducting high frequency lighting.

[0129] The electrical components 25 mainly consisting of componentshaving relatively low heat resistance, such as electrolytic condensersand film condensers, are arranged on the upside of the circuit board 24,while thin, small chip-shaped electrical components (chip components) 26having relatively high heat resistance are arranged on the underside ofthe circuit board 24. Said chip-shaped electrical components (chipcomponents) 26 consist of rectifiers (rectifying devices or diodebridges), transistors, resistors, etc. and are arranged in a packageapproximately 2 to 3 mm in thickness. The circuit board 24 has a shaperesembling a disk having a diameter less than that of a roughly circularshape with a diameter of 40 mm. Wires drawn out of the circuit board 24are connected to the electrodes 61 of the arc tube 18.

[0130] The arc tube 18 consists of three U-shaped bent bulbs 31 that aretubes having nearly identical shapes and arranged at given locations.The three U-shaped bent bulbs 31 are connected to one another viacommunicating tubes 32 and thus form a single discharge path. Anelectrode 61 having a filament coil and other necessary parts isdisposed at each end of the discharge path. Each U-shaped bent bulb 31is provided with a phosphor film, which is formed on the inner surfaceof the U-shaped bent bulb 31, hermetically contained a rare gas, such asargon, and mercury. Each U-shaped bent bulb 31 is a glass cylindricalbulb having an outer tube diameter of 10 mm and an inner tube diameterof 8 mm. In other words, the wall thickness of each bulb is 1 mm. EachU-shaped bent bulb 31 is formed into a smoothly curved U-like shapehaving a crown P by bending said glass bulb, which is 110 mm long, atthe middle portion so that the bulb 31 has a bent portion 31 a that issmoothly turned back on itself and a pair of straight portions 31 bextending parallel to each other and integrally connected to the bentportion 31 a.

[0131] The arc tube 18 is fastened to a partition plate 33, which may bereferred to as a supporting member in the claims or other parts of thespecification and serves as a fluorescent lamp fastening member as wellas a lighting circuit fastening member. The partition plate 33 isfastened to the cover 14. To be more specific, the partition plate 33has a disk-shaped base portion 34 which is provided with mounting holes34 a. The arc tube 18 is fastened to the partition plate 33 with theends of the U-shaped bent bulbs 31 respectively inserted into themounting holes 34 a and secured therein by means of, for example,bonding the regions of the bulbs to the base portion with an adhesiveagent. A fitting step portion 35 that extends upward and then outward isformed around the outer edge of the base portion 34. These members arefastened together by fitting the fitting step portion 35 in the cover 14and filling the gap between the fitting step portion 35 and the cover 14with a bonding agent 37 in such a state that the fitting edge 17 a ofthe globe 17 is fitted between the fitting step portion 35 and the cover14. A mounting edge 38 that may have a cylindrical shape rises from thetop of the fitting step portion 35, and the circuit board 24 of thelighting circuit 16 is fitted, bonded or otherwise attached to themounting edge 38.

[0132] One of the two ends of each U-shaped bent bulb 31 is sealed bymeans of line sealing with a mount, pinch sealing without a mount, orthe like. A minute tube 41 that may otherwise be called an exhaust tubeis welded to the other end of each U-shaped bent bulb 31 to dischargethe air. The minute tube 41 is designed such that it may be providedwith an amalgam if it is necessary. An electrode 61 is disposed at theend of each U-shaped bent bulb 31 that is located at an end of thedischarge path of the arc tube 18 in such a state that the filament coilof each electrode 61 is supported between a pair of copper-weld wires(lead-in wires). Via each respective dumet wire attached to the glassend of the U-shaped bent bulb 31 and thus sealed in the bulb, eachcopper-weld wire is connected to a lamp wire that is drawn out of theU-shaped bent bulb 31. Said lamp wires are electrically connected to thelighting circuit If it is necessary, one of the copper-weld wires may beprovided with an auxiliary amalgam.

[0133] In the state where the self-ballasted fluorescent lamp 10 isassembled, as shown in FIG. 13, the chip-shaped electrical components 26mounted on the underside of the circuit board 24 are located apart fromthe ends of the U-shaped bent bulbs 31 of the arc tube 18, particularlyfrom the minute tubes 41 projecting from the ends of the U-shaped bentbulbs 31. The electrical components 26 are also spaced apart from theelectrodes 61, in other words they are positioned near the U-shaped bentbulbs 31 that are not provided with an electrode 61.

[0134] When the self-ballasted fluorescent lamp 10 is assembled in themanner described above, the arc tube 18 is housed in the globe 17 at agiven position. To be more specific, in the state where theself-ballasted fluorescent lamp 10 is assembled, the crowns P of theU-shaped bent bulbs 31 are aligned at regular intervals in a circlewhose center is on the central axis of the self-ballasted fluorescentlamp 10 extending in the vertical direction, and the straight portions31 b of the U-shaped bent bulbs 31, too, are aligned at regularintervals in a circle whose center corresponds to the central axis ofthe lamp. The straight portions 31 b are aligned in a circle in such amanner that the distance W between each straight portion 31 b and itsadjacent straight portion 31 b is less than 10 mm, in other wordsshorter than the outer diameter of each U-shaped bent bulb 31.

[0135] The self-ballasted fluorescent lamp 10 structured as above hassuch characteristics that, when a rated input power is 14W, a highfrequency power of 12.5 W is applied to the arc tube 18, producing alamp current of 280 mA, a lamp voltage of 65 V and a total luminous fluxof 810 lm, which results from the use of the three band phosphor.

[0136] By mounting electrical components 25,26 on both ends the circuitboard 24 as described above, the present embodiment is capable ofreducing the size of the circuit board 24 and also reducing the diameterof the cover 14, which is located near the base 12.

[0137] As the circuit board 24 is so formed as to have an outer diameternearly identical to the inner diameter of the cover 14 and cover theinterior of the cover 14, it is possible to arrange components by makinguse of the space inside the cover 14 to the full extent and,consequently, reduce the diameter of the portion of the cover 14 nearthe base 12.

[0138] According to the present embodiment, the circuit board 24 and thearc tube 18 are positioned one directly above the other. However, as thechip-shaped electrical components 26 mounted on the side of the circuitboard 24 facing the arc tube 18 are so positioned as to not face theends of the U-shaped bent bulbs 31 of the arc tube 18, particularly theportions of the ends of the U-shaped bent bulbs 31 from which the minutetubes 41 project, the embodiment described above is capable ofpreventing interference of the arc tube with the electrical components26, limiting the influence of the heat from the arc tube, and reducingthe length of the lamp by the thickness of the chip-shaped electricalcomponents 26, i.e. 2 to 3 mm.

[0139] By disposing the electrical components 26 mounted on the side ofthe circuit board 24 facing the arc tube 18 at locations removed fromthe electrodes 61 of the arc tube 18, the embodiment is also capable oflimiting the influence that the heat generated by the electrodes 61exerts on the electrical components 26, thereby increasing thereliability of the electrical components.

[0140] As the arc tube 18 is formed by parallely arranging U-shaped bentbulbs 31 that have a U-like shape, the length of the lamp can bereduced.

[0141] By reducing the length of the bulb as well as the diameter of theportion of the lamp near the base 12, e.g. the portion extending up to30 mm from the base 12, so as to make the shape of the lamp resemble atypical PS-type electric bulb, the embodiment described above provides alamp having a shape similar to that of an incandescent lamp. Therefore,the self-ballasted fluorescent lamp 10 described above can be mounted ona luminaire designed for an incandescent lamp. Thus, the embodimentexpands the range of its usage and also improves the appearance of thelamp, permitting the lamp to be used without giving any disagreeability.

[0142] According to the embodiment described above, an arc tube 18 isformed by connecting three U-shaped bent bulbs 31. However, the shape ofthe arc tube 18 is not limited to such a configuration; the lamp lengthmay be reduced by arranging a plurality of U-shaped or H-shaped tubes,e.g. two, three or four tubes, in parallel with one another so as toform a discharge path having four, six or eight axes extending in thelengthwise direction of the lamp. Furthermore, although the lightingcircuit 16 is comprised of a single circuit board 24 that is positionedhorizontally, it may consists of a plurality of circuit boards.

[0143] A luminaire may be formed by attaching a self-ballastedfluorescent lamp 10 according to any one of the embodiments describedabove to the main body of a luminaire which is provided with a socketdesigned for an incandescent lamp or the like. Thus formed luminaire hasthe various benefits of the self-ballasted fluorescent lamp 10 describedabove.

[0144] Every configuration described above is applicable to a bent-tubetype fluorescent lamp, which may be installed in a luminaire using aball-shaped fluorescent lamp or the like.

[0145] Next, a fluorescent lamp according to yet another embodiment ofthe invention is explained hereunder, referring to drawings.

[0146] The tenth embodiment is shown in FIGS. 14 through 17, whereinFIG. 14(a) is an exploded view of a bulb of the fluorescent lamp; FIG.14(b) is an enlarged sectional view of the part A in FIG. 14(a); FIG. 15is a side view of said fluorescent lamp; FIG. 16 is a top view of same,wherein the globe of said fluorescent lamp is illustrated as if theinside contents were visible; and FIG. 17 is a sectional view of a partof said fluorescent lamp.

[0147] In the drawings, numeral 111 denotes a fluorescent lamp having ashape of a light bulb (hereinafter called self-ballasted fluorescentlamp). The self-ballasted fluorescent lamp 111 comprises a cover 113having an E26-type base 112, a lighting circuit (not shown) contained inthe cover 113, a translucent globe 114, and an arc tube 115 contained inthe globe 114. The cover 113 and the globe 114 together form an envelope19 that has such an outer shape as to have nearly the same dimensions asstandard dimensions of a typical light bulb for general illumination. Inother words, the height of the envelope ranges from approximately 110 to125 mm including the height of the base 112, while the diameter of theenvelope, i.e. the outer diameter of the globe 114, ranges fromapproximately 55 to 60 mm Further, in the explanation hereunder, theside where the base 112 is located is referred to as the lower side,while the side where the globe 114 is located is referred to as theupper side.

[0148] The cover 113 is provided with a cover body 121 that may beformed of a heat resistant synthetic resin such as polybutyleneterephthalate (PBT). The cover body 121 has an approximately cylindricalshape that flares upward. The base 112, which may be of the E26 type, isdisposed over the bottom of the cover body 121 and fastened thereto byway of bonding, crimping or any other appropriate means.

[0149] The globe 114 may be transparent or photo-diffusing milky white.The globe 114 is formed of glass, synthetic resin or the like into asmoothly curved shape nearly identical to the glass bulb of a lightbulb, with the edge of its opening fitted in an opening at the top ofthe cover 113 and fastened thereto. The luminance of the lamp may bemade more uniform by forming the globe 114 in combination with anothermember, such as a diffusion film.

[0150] A combination of such a globe 114 as described above and a bulb131, which will be described later, increases the output power of thelight irradiated in the direction of the base 112 and thereby achievesluminous intensity distribution whose characteristics are similar tothose of a light bulb for general illumination.

[0151] The lighting circuit is comprised of an inverter circuit (ahigh-frequency lighting circuit) for lighting the arc tube 115 at a highfrequency. The lighting circuit consists of an approximately disk-shapedboard on which electronic components are mounted. The maximum outerdiameter of the lighting circuit is 40 mm.

[0152] The arc tube 115 has a bulb 131. A film of phosphor 132 is formedon the inner surface of the bulb 131; The bulb 131 hermetically containsfiller gas which is a rare gas, such as argon, and mercury. The bulb 131also contains a pair of electrodes 133, which are respectively disposedat the two ends of the bulb 131.

[0153] The bulb 131 has three tubular bodies 134 a,134 b,134 c, each ofwhich may be an approximately cylindrical glass tube having an outertube diameter ranging from 8 to 11 mm and an inner tube diameter rangingfrom 6 to 9 mm and a wall thickness ranging from 0.7 to 1.0 mm, andformed into a smoothly curved U-like shape having a crown 135 by bendingsaid glass tube at the middle of its length, which ranges fromapproximately 110 to 130 mm. Therefore, each tubular body 134 a,134b,134 c has a bent portion 136 that is smoothly turned back on itselfand a pair of straight portions 137 extending parallel to each other andintegrally connected to the respective two ends of the bent portion 136.

[0154] The two ends of the tubular body 134 b, which is located at themiddle part of the bulb 131, are respectively connected throughcommunicating tubes 138 to one end of the tubular body 134 a and one endof the tubular body 134 c, which are respectively located at the ends ofthe bulb 131, so that a single continuous discharge path 139 having alength ranging from 200 to 300 mm is formed. In the state where the bulb131 is incorporated in the self-ballasted fluorescent lamp 111, thecrowns 135 (the bent portions 136) of the tubular bodies 134 a,134 b,134c are aligned at regular intervals in a circle whose center is on thecentral axis of the self-ballasted fluorescent lamp 111 extending in thevertical direction, and the straight portions 137 of the tubular bodies134 a,134 b,134 c, too, are aligned at regular intervals in a circlewhose center corresponds to the central axis of the lamp. To be morespecific, the straight portions 137 of each tubular body 134 a,134 b,134c are arranged along each respective side of a triangle that forms across section of the bulb 131. The straight portions 137 aligned in acircle are formed so that the distance between each straight portion 137and its adjacent straight portion 137 is shorter than the outer diameterof each tubular body 134 a,134 b,134 c.

[0155] The tubular bodies 134 a,134 b,134 c are respectively providedwith cylindrical minute tubes 140 a,140 b,140 c that may otherwise becalled exhaust tubes. Each minute tube 140 a,140 b,140 c communicateswith the corresponding tubular body 134 a,134 b,134 c and projects froman end thereof. However, each one of the minute tubes 140 a,140 c of thetubular bodies 134 a,134 c, which are respectively located at the twoends of the bulb 131 projects from the non-electrode end, i.e. the endopposite the end at which an electrode 133 is attached. The air isdischarged from the bulb 131 through the minute tubes 140 a,140 b,140 cor a part of these minute tubes 140 a,140 b,140 c, while the filler gasis introduced. After the filler gas has replaced the air, the bulb 131is sealed by fusing the minute tubes 140 a,140 b,140 c. FIG. 14schematically illustrates the state of the minute tubes 140 a,140 b,140c prior to fusion. Each minute tube 140 a,140 b,140 c has an open endportion 141 that communicates with the corresponding tubular body 134a,134 b,134 c. The inner diameter 12 of each open end portion 141 issmaller than the inner diameter L1 of the barrel portion of each minutetube 140 a,140 b,140 c.

[0156] Of the minute tubes 140 a,140 b,140 c of the tubular bodies 134a,134 b,134 c, the minute tube 140 a (or the minute tube 140 c), whichis located closest to either electrode 133 hermetically contains anamalgam 142. Said minute tube 140 a (or the minute tube 140 c) islocated at the non-electrode end of the tubular body 134 a (or thetubular body 134 c) at either end of the bulb 131, non-electrode endmeaning the end opposite the end at which the electrode 133 is enclosed.The amalgam 142 is enclosed in the minute tube 140 a (or the 140 c),when the minute tube is sealed. The amalgam 142 is an alloy of bismuth,indium and mercury formed into a nearly spherical shape whose diameteris greater than that of the open end portion 141 of the minute tube 140a and has the function of controlling the pressure of the mercury vaporin the bulb 131 within an appropriate range. The amalgam 142 may beformed of an alloy that consists of tin and lead in addition to bismuthand indium.

[0157] If it is necessary, an auxiliary amalgam may be disposed in thebulb 131 so as to absorb mercury floating in the bulb when the lamp isturned off, and release the absorbed mercury during the early stage oflighting, including the moment when the lighting is initiated.

[0158] Each electrode 133 has a filament coil 143 supported by a pair ofcopper-weld wires (lead-in wires) 145, each of which is fixed by a beadstem 144. Via a dumet wire 146 attached to the glass of the end of thecorresponding tubular body 134 a,134 c and thus sealed in the tubularbody, each copper-weld wire 145 is connected to a wire 147 that is drawnout of each respective tubular body 134 a,134 c. Each dumet wire 146 isenclosed in the bulb by means of a pinch seal portion 148 provided atthe end of the bulb. When the bulb 131 is installed in a self-ballastedfluorescent lamp 111, the wires 147 are connected to the lightingcircuit.

[0159]FIG. 17 illustrates the relationships that the inner diameter b ofeach communicating tube 138 and the width c of each electrode 133 havewith respect to the inner tube diameter a of the bulb 131. Thecommunicating tubes 138 are formed by joining the apertues of thetubular bodies to one another. Said apertures are formed prior to thesealing of the minute tubes 140 a,140 b,140 c, by heating and meltingthe tubular bodies and then breaking through the appropriate portions byblowing air through the tube walls.

[0160] The relationship between the inner tube diameter a of the bulb131 and the inner diameter b of each communicating tube 138 is set suchthat 0.6<a/b<1.0 in order to reduce the lamp starting voltage andimprove the rise of the light output.

[0161] The relationship between the inner tube diameter a of the bulb131 and the width c of each electrode 133 is set such that (a-c)/2<1.5mm so that the electrodes 133 generate excessive heat when the lampreaches the last stage of its life and that the generated beat melts thebulb 131 and causes the filler gas to leak from the bulb, therebyturning off the lamp to become unilluminated.

[0162] The self-ballasted fluorescent lamp 111 structured as above hascharacteristics such that, when a rated input power is 14W, a highfrequency power of 12.5 W is applied to the arc tube 18, producing alamp current of 280 mA, a lamp voltage of 65 V and a total luminous fluxof 810 lm, which results from the use of the three band phosphor.

[0163] Next, the function of the embodiment described above isexplained.

[0164] By enclosing the amalgam 142 in the minute tube 140 a, which isthe one, among the minutes tubes 140 a,140 b,140 c located at the middleportion of the bulb 131, closest to one of the electrodes 133, it ispossible to prevent the temperature of the amalgam 142 from becoming toohigh due to the influence of the heat from the electrode 133 and alsofacilitate the warming of the amalgam 142 at the initiation of lighting.

[0165] In other words, compared with the configuration where an amalgam142 is disposed at the end of the bulb 131 at which an electrode 133 isattached, the above configuration according to the present embodiment iscapable of reducing the influence that heat from an electrode 133 exertson the amalgam 142, thereby preventing the temperature of the amalgam142 from becoming too high, and also capable of limiting the pressure ofthe mercury vapor within an appropriate range. In addition, by reducingthe distances from the amalgam 142 to the two respective ends of thebulb 131, the above configuration is capable of making the pressure ofthe mercury vapor in the entire bulb 131 uniform and stable.Furthermore, compared with the configuration where an amalgam 142 isdisposed in the tubular body 134 b at the middle portion of thebulb-131, the present embodiment permits the amalgam 142 to be heatedeasily. Therefore, the embodiment is capable of improving the risingcharacteristics of the luminous flux and consequently reducing the timetaken for the luminous flux to become stable.

[0166] As described above, by enclosing the amalgam 142 in the minutetube 140 a (or minute tube 140 c), which is the one, among the minutestubes 140 a,140 b,140 c located at the middle portion of the bulb 131,closest to one of the electrodes 133, the embodiment is capable ofpreventing an unfavorable influence of the heat from the electrode 133from increasing the temperature of the amalgam 142 too much and alsofacilitating the warming of the amalgam 142 at the initiation oflighting. As a result, it is possible to limit the pressure of themercury vapor within an appropriate range and reduce the time taken forthe luminous flux to become stable when lighting is initiated.

[0167] By enclosing the amalgam 142 in the minute tube 140 a located atthe non-electrode end of the tubular body 134 a that is located at anend of the bulb 131, the embodiment is capable of maintaining thepressure of the mercury vapor within an appropriate range and reducingthe time taken for the luminous flux to become stable when lighting isinitiated.

[0168] As the inside of the minute tube 140 a, in which the amalgam 142is contained, is wider than the open end portion 141 that communicateswith the inside of the tubular body 134 a, the amalgam 142 can snugly becontained in the minute tube 140 a.

[0169] In cases where the inside of the bulb 131 is narrow, in otherwords where the inner tube diameter of the bulb 131 ranges from 6 to 9mm, it is difficult to form minute tubes 140 a,140 c, together with theelectrodes 133, at the ends (the ends where the electrodes 133 areformed) of the tubular bodies 134 a,134 c, which are respectivelylocated at the two ends of the bulb 131. On the other hand, the minutetubes 140 a,140 c can easily be formed at the non-electrode ends of thetubular bodies 134 a,134 c located at the two ends of the bulb 131.Forming the minute tubes 140 a,140 c at the non-electrode ends alsoeliminates the need of excessively reducing the diameter of the minutetubes 140 a,140 b,140 c even if the bulb 131 is narrow with its innertube diameter ranging from 6 to 9 mm.

[0170] As the three tubular bodies 134 a,134 b,134 c are arranged insuch a manner as to respectively correspond to the sides of a trianglethat forms a cross section of the bulb 131, the bulb 131 can be madeinto a compact shape without the need of being bent into a complicatedshape, such as one resembling a saddle. A compact bulb 131 formed in themanner as described above can be used for a self-ballasted fluorescentlamp 111.

[0171] In cases where the bulb 131 is narrow with its inner tubediameter ranging from 6 to 9 mm, there arise such problems that thesecondary voltage on the lighting circuit becomes too high, making itnecessary to increase the lamp initiating voltage and also slowing therise of light output, and that, when the lamp reaches the last stage ofits life, the electrodes 133 generate heat and exert a thermal influenceon the cover body 121 that supports the bulb 131. These problems can besolved by setting the relationship between the inner tube diameter a ofthe bulb 131 and the inner diameter b of each communicating tube 138such that 0.6<a/b<1.0 and the relationship between the inner tubediameter a of the bulb 131 and the width c of each electrode 133 suchthat (a-c)/2<1.5 mm.

[0172] By thus setting the relationship between the inner tube diametera of the bulb 131 and the inner diameter b of each communicating tube138 such that 0.6<a/b<1.0 so that the inner diameter b of eachcommunicating tube 138 exceeds the inner tube diameter a of the bulb131, the embodiment is capable of reducing the lamp starting voltage andimproving the rise of the light output. The relationship between theinner tube diameter a of the bulb 131 and the width c of each electrode133 is set such that (a-c)/2<1.5 mm in order to bring the inner surfaceof the bulb 131 and each electrode 133 in close proximity to each other.Therefore, when the lamp reaches the last stage of its life, heatgenerated by the electrodes 133 causes a leak in the bulb 131 and stopsthe lighting circuit, thereby causing the arc tube to becomeunilluminated.

[0173] A luminaire may be formed by attaching a self-ballastedfluorescent lamp 111 according to the embodiment described above to themain body of a luminaire which is provided with a socket designed for atypical light bulb.

[0174] If it is necessary, the embodiment may include an auxiliaryamalgam, which serves to improve the rising characteristics of luminousflux by releasing mercury at the initial stage of lighting The 11thembodiment is shown in FIGS. 18 and 19, wherein FIG. 18 is an explodedview of the bulb of a fluorescent lamp, and FIG. 19 is a circuit diagramof a lighting circuit of the fluorescent lamp.

[0175] An electrode is disposed at each end of the bulb 131 andhermetically enclosed in the bulb of an arc tube 115. Of the twoelectrodes, one is referred to as the preheating-side electrode 133 a,while the other is referred to as the non-preheating-side electrode 133b. The arc tube 115 including these electrodes 133 a,133 b is adapted tocope with a lighting circuit designed to light the lamp by preheatingonly one of the electrodes, i.e. the preheating-side electrode 133 a, bymeans of a lighting device 151 connected to a power supply E. Thelighting device 151 may be an inverter or the like.

[0176] The tubular bodies 134 a,134 b,134 c of the bulb 131 arerespectively provided with cylindrical minute tubes 140 a,140 b,140 c,each of which communicates with the corresponding tubular body 134 a,134b,134 c and projects from an end thereof. Of these minute tubes, theminute tubes 140 a,140 c of the tubular bodies 134 a,134 c, which arerespectively located at the two ends of the bulb 131, project from thenon-electrode ends, i.e. the ends opposite the ends at which theelectrodes 133 a,133 b are attached.

[0177] If it is necessary, the minute tube that is closest to thepreheating-side electrode 133 a, i.e. the minute tube 140 a, may containa main amalgam 142 a, which serves as the amalgam referred to in theclaims and other parts of this specification and has the sameconfiguration as that of the amalgam 142 described above.

[0178] The pair of copper-weld wires 145 of each electrode 133 a,133 bis provided with an auxiliary amalgam 152 a, which is enclosed in thebulb 131 together with the corresponding electrode 133 a,133 b. Eachauxiliary amalgam 152 a consists of a foil of such a metal as stainlesssteel or a nickel, or a metal having a high melting point, such asmolybdenum, tantalum or niobium, and indium bonded to the surface ofsaid metal foil by means of plating or vapor deposition.

[0179] An auxiliary amalgam 152 b is disposed at an end of the tubularbody 134 that is located at the middle portion of the bulb 131. The endwhere the auxiliary amalgam 152 b is disposed is located opposite theminute tube 140 b and at a long distance from the main amalgam 142 a.The auxiliary amalgam 152 b has mercury vapor pressure characteristicssimilar to those of the auxiliary amalgams 152 a; it absorbs mercuryvapor when the lamp is turned off and releases mercury vapor when thelamp is turned on.

[0180] With the configuration as above, by enclosing the main amalgam142 a in the minute tube 140 a, which is the closest minute tube to thepreheating-side electrode 133 a and is located at the non-electrode endof the tubular body 134 a at one end of the bulb 131, the embodimentmakes the main amalgam 142 easy to be warmed by the heat from thepreheating-side electrode 133 a at the initiation of lighting andimproves the rising characteristics of luminous flux.

[0181] By means of the auxiliary amalgams 152 a disposed at theelectrodes 133 a,133 b and the auxiliary amalgam 152 b disposed halfwaybetween the electrodes 133 a,133 b, the embodiment is capable ofreleasing the mercury at the initial stage of lighting, therebyimproving the rising characteristics of luminous flux.

[0182] As the auxiliary amalgam 152 b having mercury vapor pressurecharacteristics similar to those of the main amalgam 142 a and theauxiliary amalgams 152 a is enclosed in the bulb 131, the auxiliaryamalgam 152 b works in conjunction with the main amalgam 142 a and theauxiliary amalgams 152 a to maintain the pressure of the mercury vaporin the bulb 131 within an appropriate range and reduce the time takenfor the luminous flux to become stable when lighting is initiated.

[0183] Next, the 12th embodiment of the invention is shown in FIG. 20,which is a top view of a fluorescent lamp, with the globe of saidfluorescent lamp illustrated as if the inside contents were visible.

[0184] A bulb 131 having a curved discharge path 139 is formed byconnecting a plurality of U-shaped tubular bodies 134 a,134 b,134 c insuch a manner that the planes defined by these tubular bodies 134 a,134b,134 c face one another and extend in parallel.

[0185] As the distance L3 between the electrode 133 of each tubular body134 a,134 c and the other end of the tubular body 134 a,134 c, i.e. theend at which the electrode is not provided, is greater than the distanceL4 between the electrode 133 and the corresponding end of the tubularbody 134 b adjacent to the electrode 133, disposing an amalgam 142 (or amain amalgam 142 a) in the crown of the tubular body 134 b adjacent tothe electrode 133 is more effective to improve vaporization of themercury.

[0186] In any one of the embodiments described above, the bulb may beformed by connecting four, five or more tubular bodies.

INDUSTRIAL APPLICABILITY

[0187] As described above, a fluorescent lamp, a self-ballastedfluorescent lamp and a luminaire according to the present invention aresuitable for a compact structure, in particular, a structure which usesa fluorescent lamp in place of a typical light bulb.

1. A fluorescent lamp including: a bulb having a bent discharge path,which is formed by connecting a plurality of tubular bodies in series,and a plurality of minute tubes located at the middle of the dischargepath and communicating therewith; a phosphor applied to the innersurface of the bulb; filler gas hermetically contained in the bulb;electrodes respectively disposed at the two ends of the bulb in such amanner as to be enclosed in the sealed bulb; and an amalgam enclosed ina minute tube closest to either electrode.
 2. A fluorescent lamp asclaimed in claim 1, wherein: one of the electrodes attached to the twoends of the bulb so as to be contained in the sealed bulb is apreheating-side electrode, i.e. an electrode disposed at the end wherepreheating is conducted, while the other electrode is anon-preheating-side electrode, i.e. an electrode disposed at the endwhere preheating is not conducted; and the amalgam is enclosed in theminute tube which is closest to the preheating-side electrode.
 3. Afluorescent lamp as claimed in claim 1 or claim 2, wherein the open endportion through which said minute tube communicates with thecorresponding tubular body is narrower than the interior of the body ofthe minute tube, in which said amalgam is enclosed.
 4. A fluorescentlamp including: a bulb having an inner tube diameter ranging from 6 to 9mm and a bent discharge path, which is formed by connecting a pluralityof tubular bodies in series, each tubular body that is located at an endof the bulb being provided with a minute tube formed at thenon-electrode end of the tubular body, i.e. the end where an electrodeis not disposed; a phosphor applied to the inner surface of the bulb;filler gas hermetically contained in the bulb; and electrodesrespectively disposed at the two ends of the bulb in such a manner as tobe enclosed in the sealed bulb.
 5. A fluorescent lamp as claimed inclaim 4, wherein an amalgam is contained in the minute tube that isprovided at the non-electrode end of a tubular body located at an end ofthe bulb.
 6. A fluorescent lamp as claimed in any one of the claims fromclaim 1 to claim 5, wherein an auxiliary amalgam is disposed in thebulb.
 7. A fluorescent lamp as claimed in any one of the claims fromclaim 1 to claim 6, wherein the tubular bodies of the bulb arepositioned in such a manner that the tubular bodies respectivelycorrespond to the three sides of a triangle when viewed in a crosssection.
 8. A self-ballasted fluorescent lamp including: a fluorescentlamp as claimed in any one of the claims from claim 1 to claim 7; and alighting device for lighting said fluorescent lamp.
 9. A self-ballastedfluorescent lamp including: an arc tube which is formed by parallelyarranging a plurality of U-shaped bent bulbs having an inner tubediameter ranging from 6 to 9 mm in such a manner that the height of thebulb and the length of the discharge path respectively range from 50 to60 mm and from 200 to 300 mm and that the lamp has a total luminous fluxof not less than 700 lm and a lamp efficiency of not less than 60 lm/Wwhen the lamp is lit at the lamp power of 7 to 15 W; an envelope havinga cover that includes a base and is adapted to permit said arc tube tobe attached thereto, the height of the envelope ranging from 110 to 125mm including the height of the base; and a lighting circuit contained inthe cover.
 10. A self-ballasted fluorescent lamp including: an arc tubeformed by parallely arranging a plurality of U-shaped bent bulbs, eachof which has an outer tube diameter ranging from 8 to 11 mm, a tube wallthickness ranging from 0.7 to 1.0 mm and a smoothly curved crown; acover including a base that is adapted to permit said arc tube to beattached thereto; and a lighting circuit contained in the cover.
 11. Aself-ballasted fluorescent lamp including: an arc tube formed byparallely arranging a plurality of U-shaped bent bulbs, each of whichhas a bent portion and straight portions; a cover including a base thatis adapted to permit said arc tube to be attached thereto; and alighting circuit which includes a circuit board having the maximum widthranging up to 1.2 times the maximum width of the arc tube, said maximumwidth of the arc tube being the dimension along which the U-shaped bentbulbs are arranged, said lighting circuit contained in the cover in sucha manner that the circuit board is positioned with one of its sidesfacing all the ends of the straight portions of the arc tube andprovided with components having relatively high heat resistance mountedon the side of the circuit board facing the arc tube and componentshaving relatively low beat resistance mounted on the opposite side ofthe circuit board.
 12. A self-ballasted fluorescent lamp as claimed inclaim 11, wherein said components having relatively high heat resistanceof the fluorescent lamp are chip-shaped rectifying devices.
 13. Aself-ballasted fluorescent lamp including: a cover having a base; alighting circuit contained in the cover; a globe having a nearlyidentical shape as a typical light bulb and attached to the cover, andan arc tube which is contained in the globe and has three or moreU-shaped bent bulbs, each of which has a smoothly curbed crown, saidU-shaped bent bulbs connected to one another in series and arranged sothat their crowns are aligned in a circle and face the inner surface ofthe globe and that the U-shaped bent bulbs are spaced apart at adistance not exceeding the outer diameter of each bulb.
 14. Aself-ballasted fluorescent lamp including: an arc tube formed byparallely arranging a plurality of U-shaped bent bulbs having an outertube diameter ranging from 8 to 11 mm, the maximum width of the arctube, i.e. the dimension along which the U-shaped bent bulbs arearranged, ranging from 32 to 43 mm; a cover including a base that isadapted to permit said arc tube to be attached thereto; a lightingcircuit contained in the cover; and a globe having a maximum outerdiameter limited in the range from 55 to 60 mm and attached to the coverwith said arc tube enclosed in the globe in such a manner that A2>A1≧A3,wherein A1 represents the minimum distance between the globe and eachcrown of the arc tube, A2 the minimum distance between the maximumdiameter portion of the globe and the arc tube, and A3 the minimumdistance between the base end of the globe and the arc tube.
 15. Aself-ballasted fluorescent lamp as claimed in claim 14, wherein A1 isset in the range from 2 to 8 mm, A2 in the range from 3 to 13 mm and A3in the range from 2 to 8 mm.
 16. A self-ballasted fluorescent lamp asclaimed in claim 14 or claim 15, wherein the outer shape of the lampresembles a typical light bulb for general illumination.
 17. Aself-ballasted fluorescent lamp as claimed in any one of the claims fromclaim 14 to claim 16, wherein the self-ballasted fluorescent lampincludes: a supporting member for supporting the arc tube; and a bondingagent for bonding the arc tube, the globe and the supporting member toone another.
 18. A self-ballasted fluorescent lamp as claimed in any oneof the claims from claim 9 to claim 17, wherein the U-shaped bent bulbsof the arc tube are arranged in such a manner that the cross sections ofthe U-shaped bent bulbs give the appearance of a triangle.
 19. Aself-ballasted fluorescent lamp as claimed in any one of the claims fromclaim 9 to claim 18, wherein: the distance w1 between the two straightportions of each U-shaped bent bulb is so set as to be nearly identicalto the distance w2 between each straight portion of a U-shaped bent bulband the U-shaped bent bulb that is adjacent to said straight portion;and the distances w1,w2 are respectively limited in the range from 1 to5 mm.
 20. A self-ballasted fluorescent lamp as claimed in any one of theclaims from claim 9 to claim 19, wherein the lighting circuit includes:a half-bridge type inverter main circuit having at least a pair oftransistors consisting of an N-channel transistor and a P-channeltransistor, which are connected in series with each other to an inputpower supply and serve as the main switching element for generating ahigh frequency voltage; a ballast choke connected to the inverter maincircuit so as to light the arc tube in stable conditions; and a controlmeans which has a secondary winding magnetically connected to theballast choke and shared by the N-channel transistor and the P-channeltransistor so that the control means serves to control the transistorsby means of the secondary winding.
 21. A self-ballasted fluorescent lampincluding: an arc tube; a cover having a base; and a lighting circuitthat has a circuit board and electrical components mounted on both sidesof the circuit board in such a manner that the circuit board iscontained in the cover and faces the ends of the arc tube and that theelectrical components mounted on the side facing the arc tube are sopositioned as to not be aligned with the ends of the arc tube.
 22. Aself-ballasted fluorescent lamp including: an arc tube; a cover having abase; and a lighting circuit that has a circuit board and electricalcomponents mounted on both sides of the circuit board in such a mannerthat the circuit board is contained in the cover and faces the ends ofthe arc tube and that the electrical components mounted on the sidefacing the arc tube are so positioned as to not be aligned with theminute tubes of the arc tube.
 23. A self-ballasted fluorescent lamp asclaimed in claim 21 or claim 22, wherein the outer diameter of thecircuit board is nearly identical to the inner diameter of the cover.24. A self-ballasted fluorescent lamp as claimed in any one of theclaims from claim 21 to claim 23, wherein the electrical componentsmounted on the side facing the arc tube are positioned apart from theelectrodes of the arc tube.
 25. A luminaire including a self-ballastedfluorescent lamp as claimed in any one of the claims from claim 8 toclaim 24.